Math/Utils - various cleanup and deprecations/moves

There are no known breaking changes.

- Timer
  - Uses standard Math.min/Math.max (it's better 2, 3 items).

- Math
  - Updated documentation
  - Marked various Math functions as deprecated, proxying as appropriate
    - Array-based functions -> ArrayUtils
    - RNG-based functions -> Utils
    - Updated core-usage
    - floor/ceil should not be used (alternatives provided)
  - Altered for some equivalencies
  - Also fixes some assorted issues
  - Marked a few internal functions as private

- Utils
  - Moved polyfills to their own file for better visibility
  - Moved array functions to ArrayUtils and marked proxies as deprecated

- Created Phaser.ArrayUtils for array-related functions

- polyfills moved to their own file
  - Functions given function names
  - Added Math.trunc