DGEngine v0.1.21

Release for Windows

- update minimum SFML version to 2.4 (fix deprecated get/setColor)
- embed sfeMovie
- update cmake to add FFmpeg FindFFMPEG.cmake
- update deprecated code for FFMPEG3 upgrade in sfeMovie (90%)
- remove unused code from sfeMovie (SubtitleStream)

- add isUsable to item
- add touch support (untested)
- add UIText interface
- execute action given drawable id and action name
- refactor buttons
- refactor cel decoding (fix small font)
- refactor input events code
- refactor setText actions into one (text.setText)
- refactor StringButton, Text2
- update android minimum version
- update itemClass description to support skipping matches
- update UIObject interface to add method to get action

- update gamefiles
- add F1-F6 keyboard actions to add/remove gold, life, mana (for testing purposes)
- resize level panel if user panels are open/closed and if size = 640x480 and stretchToFit = true
- update item prefixes and descriptions
- update level right click

Note: This is a work in progress. Some things aren't perfect and that's known.
Delete previous saves to avoid error caused by changes.