API / documentation consistency updates

- The `disabled` property of various input classes has been inverted to `enabled`.
  Direct/internal usage of `disabled` has been transformed to `!enabled`.
- A `disabled` get/set property has been added to wrap `enabled`, and marked as @deprecated
  This ensures current API compatibility.
Updated documentation per current Phaser tag usage
Merge pull request #1257 from pnstickne/wip-1191

Input "enabled/disabled" API and documentation consistency updates