Xenoids Demo update to version d0.18

Xenoids Demo has been updated to version d0.18
Changes:
- Transfer of the project to a newer version of the game engine.
- Changes in the visual design: more volumetric light sources, changed the fog effect, added an effect when using CCTV cameras.
- Improved optimization.
- Some interface sounds have been replaced.
- Changes in the balance.
- Fixed several bugs.