Add release notes for 15.0.1.0 & 15.0.2.0
Use JEP-322 Time-Based Versioning so we can handle a future 11.0.9.1-like release correctly.
Still use 15.0.x rather than 15.0.x.0 for file naming, as the trailing zero is omitted from tags.
Cleanup debug package descriptions and version number placement.
Remove unused patch files.
