Allow the `generate` goal to pull info out of source files

**Is your feature request related to a problem? Please describe.**
The `enhance` goal may cause problems in environments with incremental build mechanisms. In the best case, it may schedule a second build - in the worst case infinite builds.

**Describe the solution you'd like**
The `enhance` goal picks up information from Java source files and adds it to the Java annotations embedded in the class files. If the `generate` goal could pick up that information and put it directly into the generated XML descriptors, it might not be necessary at all to use the `enhance` goal to post-process the class files.

**Additional context**
See https://github.com/apache/uima-uimaj/issues/428

Start by tracing the existing generate and enhance goals and how they obtain information from Java source files. Compare the enhance output in Java annotations embedded in class files with the generated XML descriptors, using issue 428 for context. Done means generate includes the needed information in the descriptors without requiring enhance or causing incremental-build loops.

Written by the indexing model from the issue text.