Big UDMF thing overhaul
- Thing behavior args are separated from thing action args.
- Separate SRB2 style object scale from ZDoom style sprite scale.
- Before, these used conflicting variable names, and the editor sucked ass at reloading it properly.
- Add UDMF versioning system, to make future-proofing old maps with changes like these easier in the future.
- Converting older maps does not happen currently.
- Port many of the action arg enhancements from regular UDMF.
- Checkboxes to switch between the string version of arg 1 and 2.
- Script-related actions show available script names.
- Script-related actions display the script's argument names in the editor.
- Display the thing's sprite & object scales in 2D and 3D mode.