Break out applib and JDO services into modules

... so that in future these can be released independently of core; and to reduce configuration (isis.properties file).

Some principles:

• minimize the amount of configuration required; by exploiting @DomainService annotation, in many cases it should be sufficient to simply add the appropriate module to the classpath, and let the service be auto-reigstered.
• "on the other hand", don't (without some safety checks) want to start automatically registering services that might substantially change behaviour of the system. For example, the JDO services - audit, command, publishing - all require explicit configuration in isis.properties. Automatically registering these might be "too much, too soon".

Thus:

• In services containing only programmatic or hidden services ("system services, repos") then these should be annotated with @DomainService; thus they are configured and registered automatically if added to the classpath.
• In services containing only "contributions" can (probably safely enough) be annotated with @DomainService; thus they are configured and registered automatically if added to the classpath.
• any menu UI services should NOT be annotated with @DomainService, because the developer may want to have more fine-grained control on how the UI appears.

~~~~~~
No change for the following services:

core request-scoped services; already annotated with @DomainService, and so always available

• CommandContext (no UI; applib implementation; populated by runtime if available) - UPDATED JAVADOC
• Bulk.InteractionContext (no UI; applib implementation; not used by runtime) - UPDATED JAVADOC
• Scratchpad (no UI; applib implementation; not used by runtime) - UPDATED JAVADOC
• QueryResultsCache (no UI; applib implementation; not used by runtime) - UPDATED JAVADOC

core singleton services; already annotated with @DomainService, and so always available

• MementoServiceDefault (no UI; runtime implementation; used implicitly by runtime for commands) - UPDATED JAVADOC
• BookmarkServiceDefault (no UI; runtime implementation; used implicitly by runtime for commands) - UPDATED JAVADOC, now non UI, separated out out contributions
• XmlSnapshotServiceDefault (no UI; runtime implementation; not used by runtime) - UPDATED JAVADOC
• ClassDiscoveryServiceUsingReflections (no UI; applib implementation; not used by runtime) - UPDATED JAVADOC
• ClockService (no UI; applib implementation; not used by runtime) - UPDATED JAVADOC

~~~
These services should changed to be annotated annotated with @DomainService (because JDO is now core):

• IsisJdoSupportImpl (no UI; not used by runtime) - NOW ANNOTATED; UPDATED EXAMPLE APPS (isis.properties, *SystemInitializer for integ tests
• EventBusServiceJdo (no UI, used by runtime if available) - NOW ANNOTATED; UPDATED EXAMPLE APPS (isis.properties, *SystemInitializer for integ tests

~~~
IsisJdoSupport API should move from the jdo-applib to applib; - DONE.

~~~~~~
The following are new (Maven) modules.

Some notes:

• If a service can be used by runtime, then its API is defined in applib; the module therefore contains only the impl. Most of the modules below fall into this category.
• If a service is completely standalone from the framework, then it defines its own API (in an "applib" submodule) and its own impl. An example of this is isis-module-settings, which defines AppSettings and UserSettings.

isis-module-wrapper (used by integtestsupport)

• WrapperFactoryDefault (no UI; already @DomainService; rename core-wrapper implementation); DONE, UPDATED pom.xml in example apps;

isis-module-command-jdo - MOVED, UPDATED.

• CommandServiceJdo (used by runtime if available, so API in applib) - DECIDED NOT TO MAKE INTO @DomainService FOR NOW.
• CommandServiceJdoContributions (UI, not used by runtime)
• CommandServiceJdoRepository (no UI, supporting service for ...Contributions); - NOW ANNOTATED AS @DomainService; UPDATED EXAMPLES
• BackgroundCommandServiceJdo (UI visible, not used by runtime but prereq for background service) - NOW ANNOTATED AS @DomainService; UPDATED EXAMPLES
• BackgroundCommandServiceJdoContributions (UI visible, not used by runtime)
• BackgroundCommandServiceJdoRepository (not visible, supporting service for ...Contributions); - NOW ANNOTATED AS @DomainService; UPDATED EXAMPLES

isis-module-audit-jdo - MOVED, UPDATED.

• AuditingServiceJdo (used by runtime if available, so API in applib) - DECIDED NOT TO MAKE INTO @DomainService FOR NOW
• AuditingServiceJdoContributions (UI, not used by runtime)
• AuditingServiceJdoRepository (not visible, supporting service for ...Contributions); - NOW ANNOTATED AS @DomainService; UPDATED EXAMPLES

isis-module-background

• BackgroundServiceDefault (used by runtime if available, so API in applib; requires BackgroundCommandService); CAN'T SAFELY BE A @DomainService BECAUSE OF DEPENDENCY ON impl. of BackgroundCommandService

isis-module-publishing-jdo

• PublishingServiceJdo (used by runtime if available, so API in applib)
• PublishingServiceJdoContributions (UI, not used by runtime)
• PublishingServiceJdoRepository (not visible, supporting service for ...Contributions); - NOW ANNOTATED AS @DomainService; UPDATED EXAMPLES

isis-module-publishingeventserializer-ro

• RestfulObjectsSpecEventSerializer (not visible, used by publishing service); - NOW ANNOTED AS @DomainService; UPDATED EXAMPLES

isis-module-devutils (not used by runtime, standalone); DONE

• applib
  > DeveloperUtilitiesService
• impl
  > DeveloperUtilitiesServiceDefault (metamodel impl)

isis-module-settings (not used by runtime, standalone); DONE

• applib
  > ApplicationSettingsServiceRW
  > UserSettingsServiceRW
• impl-jdo
  > ApplicationSettingsServiceJdo (UI, not used by runtime)
  > ApplicationSettingsServiceHidden (not UI, not used by runtime)
  > UserSettingsServiceJdo (UI, not used by runtime)
  > UserSettingsServiceHidden (not UI, not used by runtime)

in addition:

• move IsisJdoSupport APi into core-applib *; DONE; HAVE REMOVED jdo-applib completely... updated pom.xml for example apps.
• EventBusServiceDefault can be deprecated, since its subclass EventBusServiceJdo is always available; DONE

• have decided to leave ExceptionRecognizerCompositeForJdoObjectStore to be explicitly registered; likelihood that this will require customisation in some cases. (used by runtime if available)