Quality of life enhancements for 1.0.1

[TheSandvichMaker]

Just writing these down here for reference:

• [x] Saving/loading of light settings for global lights and weapon lights.
• [x] Fix behaviour in the material editor when trying to save a material with its parameters set to default.
• [x] Add ability to change texture paths in material editor.
• [x] Add options for configuring headlights.
• [x] Add menu option for bilinear filtering.
• [x] Fix NaNs that can show up in shading.
• [x] Fix quick save loading
• [x] End level cutscenes are not lit properly
• [x] Spaceship in end-level cutscene is not visible
• [x] Weapons seem to shoot at changing intervals
• Seems to be a later fix of a source port, the OGL version from DXX-Retro does the same
• [x] UAV barriers for ping-pong render targets do not work correctly
• [x] Empty energy bar visible through UI elements