Implement absolutez flag for things & support flip flag

See merge request STJr/UltimateZoneBuilder!9

Added action to change the index of linedefs, things, sectors, and vertices. Can be accessed through a shortcut (not bound by default) or the menu of the respective mode (#903)

- Add category-wide args to individual things, since they don't work (yet)
- Remove 3D mode start since it doesn't seem to work anyway

Draw NiGHTS track, zoom tubes and polyobjects in classic modes

See merge request STJr/UltimateZoneBuilder!8

- Change some category colors
- Use newly added internal sprites

- Disable Visual Mode view stretching
- Disable increased texture brightness in classic modes
- Increased default Visual Mode FOV from 80 to 90

Update config

See merge request STJr/UltimateZoneBuilder!7