Supporting local and add-on Generator "Override" jars

<From an e-mail proposal talked about on the torque-dev list>

I've been looking at how to package, document, contribute
my betwixt map/dtd generation code. As Thomas pointed out,
it's not truely mainstream Torque but might be a useful
addon. Anyway, this got me thinking about how to best
support template and/or generator local modifications or
add-on.

If the generator build scripts supplied by the Torque
distro had classpaths that first tried to add any
*-override.jar files before the distro files, then
Templates and generator classes could easily be locally
overriden. This is trivial to do with the Ant
torque-build.xml. I assume that it would be easy in Maven?

If no *override.jar files exist, it's a standard install.
But if you've got local changes to implement or want to
use a supplied add-on, just add *override.jar files to the
correct directory(s) and use the standard generation
processes.

IMHO, this seems cleaner than trying to maintain a full
customized template or generator distros. If a new
version comes out, just grab the standard, check for
any gottcha's between it and your modified code, add back
in your override jars. All the benefits of a new version
with your local mods included.

In a lot of cases, like changes to sql generation
templates (e.g. MySQL Table options ) or new db
adaptor support (like Informix/MSSQL7), this will be
very easy. These areas don't change a lot or are
mostly new templates.

It also allows for easier add-on contributions. An add-on
could be supplied as a set of jars that are simply put in
the correct directories using common How-To instructions.
The add-in supplier just needs to document any additional
settings.

It's not perfect since add-on's can override each other
and break... but it's better than it was.