[DanielThomas]

Changes

• Add ja describe types for listing compiler-resolved types referenced by a Java type or source file.
• Add ja find callees and ja find supertypes.
• Resolve relative source and class file targets against the working directory.
• Include the new commands in help, completion, module project, Gradle, and Maven coverage.

Validation

• ja test --all: 491 passed, 3 skipped (494 discovered).
• Exercised all three commands against Ja's own source.
• git diff --check passed.