RFR: JDK-8298060: Fix precision bug in gesture recognizer classes [v3]

[John Hendrikx]

> This includes a fix for the precision problem we've found as part of the graphics warnings clean ups.
> 
> I've included two commits, one with just the minimal fix, and one with the clean ups. I can drop off the 2nd commit if it is deemed to be of no added value.

John Hendrikx has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - Merge remote-tracking branch 'upstream/master' into feature/precision-problem-in-gesture-recognizers
 - Make RotateGestureRecognizer easier to test
 - Revert all changes to RotateGestureRecognizer
 - General clean ups
   
   - Made constants written in capitals final
   - Made fields final that can be final
   - Made fields and methods private that can be private
   - Renamed constants that aren't constant to camel case
   - Fixed spelling errors
   - Re-ordered fields (statics at the top)
   - Removed redundant initial values
   - Removed unused fields and parameters
   - Optimized imports
   - Removed commented out code
 - Fix precision problems in gesture recognizers

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

Changes: https://git.openjdk.org/jfx/pull/966/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=966&range=02
  Stats: 530 lines in 7 files changed: 377 ins; 36 del; 117 mod
  Patch: https://git.openjdk.org/jfx/pull/966.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/966/head:pull/966

PR: https://git.openjdk.org/jfx/pull/966