Add test-jar functionality, options for JAR tasks

Include the ability to add the tests as a JAR similar to the test-jar goal in maven,
as well as providing the ability to optionally specify which of sources, javadoc and
tests should be included in the list of artifacts to upload to a Nexus repository.

Defaults in the convention have changed to _not_ include any of the three by default;
while this changes the default previous behavior, it seems appropriate to opt-in, not
opt-out, on a per-project basis.

Minor: correct camel-casing of 'JavaDoc' to reflect common case rules, make consistent
the references internally.
Remove unused methods from plugin

By moving the artifact additions into the configure methods, the addArtifacts
method is no longer relevant. Keeping it clean.
Merge branch 'feature/improve-jar-tasks' into develop
Make JAR tasks configurable.
Added integration tasks and change JAR task configuration behavior.