-Added HUD icons for nZombies Rezurrection

-Updated to keep up with it's base.

Appearance:
Fixed missing texture on the visor.

Back end:
Moved base code to the Rebirth gas mask addon.

i think i uploaded the wrong file to the workshop last time, this should fix it.

Fixed errors when spawning the helmet and dying with it.

- Fixed error with net message bit count.
- Added LODs to the worldmodel.

- Made this addon into a base for others to make their own gas masks.
- Improved code for checking damage type, now supports hits with multiple types.
- No longer uses the "pp_mat_overlay" console command for the screen overlay.
- Uses net messages to let other clients know when to draw the helmet.

- Further code optimizations.
- DMG_CHEMICAL no longer exists, replaced with DMG_ACID.

- Fixed errors that would occur in gamemodes other than nZombies
- Fixed all animations being replaced with taking the helmet off

HOTFIX - The previous one didn't work every time. This one should be good.

HOTFIX - Fixed players only being able to use the PES once