Adding various features to improve user experience

Hello! Here is what has been added to the game with this patch:
- Added Sound Options menu when in mission.
- Added a brief auto explanation of controls that pops-up at the beginning of the first mission.
- Added menu option that explains briefly what each exterminator' skills are.
- Added retro roughness look
- Moved some spawns that where annoying where they were...
- Minor change on Ghoulraiders' AI.