RFR: JDK-8297414: Remove easy warnings in javafx.controls

[John Hendrikx]

Note: I ran into a `javac` compiler bug while replacing types with diamond operators (ecj has no issues).  I had two options, add a `SuppressWarnings("unused")` or to use a lambda instead of a method reference to make `javac` happy.  I choose the later and added a comment so it can be fixed once the bug is fixed.  I've reported the issue here: https://bugs.openjdk.org/browse/JDK-8297428

- Remove unsupported/unnecessary SuppressWarning annotations
- Remove reduntant type specifications (use diamond operator)
- Remove unused or duplicate imports
- Remove unnecessary casts (type is already correct type or can be autoboxed)
- Remove unnecessary semi-colons (at end of class definitions, or just repeated ones)
- Remove redundant super interfaces (interface that is already inherited)
- Remove unused type parameters
- Remove declared checked exceptions that are never thrown
- Add missing `@Override` annotations

-------------

Commit messages:
 - Add workaround for JDK-8297428 (javac compiler type inference bug)
 - Remove unused imports
 - Remove unnecessary casts
 - Remove unnecessary semi-colons
 - Remove redundant super interfaces
 - Use diamond operator where possible
 - Remove declared exceptions that are never thrown
 - Remove superfluous instanceof tests
 - Add missing @Override annotations
 - Remove unused type parameters
 - ... and 5 more: https://git.openjdk.org/jfx/compare/a0ea8743...1c796a13

Changes: https://git.openjdk.org/jfx/pull/959/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=959&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297414
  Stats: 2210 lines in 319 files changed: 81 ins; 317 del; 1812 mod
  Patch: https://git.openjdk.org/jfx/pull/959.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/959/head:pull/959

PR: https://git.openjdk.org/jfx/pull/959