Restore plugins from config.xml

CLI should be able to restore plugins that are listed on the top level config.xml.

Essentially an entry like below, should cause the org.apache.cordova.core.console plugin version 0.2.8 to be installed from registry. If version is omitted is should just use the latest available from registry.
<feature name="Console">
<param name="id" value="org.apache.cordova.core.console" />
<param name="version" value="0.2.8" />
</feature>

Moreover we should add a save plugins command to save the currently installed plugins to config.xml