[build] Clean up publication.

• Remove the jar artifiact so it doesn't get uploaded
• Map the modulename/groupname props to “archivesBaseName” and “group” in the Gradle model
[build] Fix deleteCopiedMods task.

It was deleting files during configuration time.
[build] Fix issue where copyMod did not depend on compileJava.

This meant that unless the compile step was explicitly invoked before packaging there would be no class files.
[build] Remove some path and dependency coupling by utilising the model.
[build] Filter the test classpath in a non lossy manner.

This removes the need to explicitly state the dependency test → testClasses.