Cleanup warnings and merge new unit tests

[stleary]

What problem does this code solve?

• Fixed some compiler warnings
  • Added @SuppressWarning annotations to ParserConfigurationo and derived class methods, as needed
  • Added descriptions as needed to param and return docstrings as needed
  • Added <> to ArrayList ctors in unit test WeirdList
  • Added unchecked warning flag to pom.xml for greater visibility of this warning
• Pulled in unit tests from Add a config flag to disable whitespace trimming #832, lest they be lost

Notes:
Return type T extends ParserConfiguration is a clever design, but it seems to require suppressing Unchecked warnings in the methods and overrides, resulting in a code smell. This was missed in the initial review. The design is not being changed at this time because it would require changes to existing API methods. If anyone has ideas about how to mitigate this without changing the API, please let me know.

Does the code still compile with Java6?
Yes

Risks
Low

Changes to the API?
No

Will this require a new release?
No

Should the documentation be updated?
No

Does it break the unit tests?
No, some new tests were added

Was any code refactored in this commit?

Review status
APPROVED - by myself

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