Describe the PR

• Update UnusedAssignment
• As described on [java] Java-grammar progress document #2701 I think the reaching definitions analysis may be useful for other rules, and maybe for the symbol table. This is work for later, but reenabling the tests of the rule is good for future refactorings.

This also fixes a bug with call chains. I'll open an issue to describe it (-> #2796)

Related issues

• An item of [java] Java-grammar progress document #2701
• Fix [java] UnusedAssignment false positive with call chains #2796

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by travis)
• Added (in-code) documentation (if needed)