Ver. 1.2.6: Modifier state persistence and negative colour tint fix

This is a generally recommended bugfix update.

Fixes:

• Fixed modifier state persistence across loading.
• Fixed negative colour tint.
• Fixed the wording of some console info and warning messages.
• If skewX, skewY or angle are set after construction of a ModifierDefinition, they now always correctly activate or deactivate the transform calculation.

Revisions:

• This plugin is now tested with RPG Maker MZ version 1.9.0.
• The “Targets:” parameter now defaults to ["REQUIRED"] as reminder to not forget it. (Only when creating a new rule in the plugin settings.)
• Changelog formatting of the previous release.
• JSDoc clarification and formatting.