remove duplicate models/materials/sounds etc which are in base game files

aprim fools

Add custom loading screens to all maps

Changes map4:
- removed >85% of sprites for optimisation

Add 4th map - AMBER Complex. It is 3 previous maps merged into one. Can be unstable on some challenges which spawn a lot of entities.

Changes map1:
- fix last objective gets completed before other 4 are completed
- add elevator going down animation
Changes map2:
- add elevator going down animation
Changes map3:
- make railings in upload data room shootable-through
- add elevator going down animation

Changes map1:
- add blue colorcorrection
- make water below bridge not reflect entities (there were huge fps drops)
- remove couple railings at beginning
- add bulletblock to grate in bridge to prevent gl bug
- add afk killer in very beginning
- add low density fog in beginning
- make map compatible with darkness challenge
Changes map2:
- make map compatible with darkness challenge
- prevent dynamic doors casting shadows
- fix badly alligned vent textures in couple areas
Changes map3:
- attempt to fix navigation issue with aliens getting stuck inside their moveto targets in two places
- make water not reflect entities (more fps, yay)
- bit more decoration