uv3 eclipse plugins build missing uimaj-ep-jcasgenp

The built eclipse update site is missing the uimaj-ep-jcasgen plugin. The build correctly built it, the publishing steps failed at the very end. Finally traced to an issue with the version level of the maven-bundle-plugin.

This was noticed before when UIMA-5202 was worked on, because another plugin (the uimaj-ep-configurator) also got dropped, when, as part of 5202, the maven-bundle-plugin was upgraded to 3.0.1. This was done to fix errors that occurred when the bundle plugin was scanning Java 8 classes and looking up things related to that.

Fix this by restoring the default back to 2.3.7, and just overriding this to 3.0.1 for the one plugin needing it, the uimaj-ep-runtime plugin and the one plugin not building in Eclipse env: uimaj-ep-launcher.