Added mask code and some mask items.

Removed the flashlight item, it was a wasted attachment slot anyway.

Added mask code that is actually just a copy of the hat code. So
defining them is just the same with DefineMaskItem and
SetMaskOffsetsForSkin.

Added all the important code for saving masks, admin duty removal, death
drop etc.

Made Gas Mask and Zorro Mask mask items, also added a Hockey Mask (which
replaces the old Ammo Tin item)

Changed max uptime to 9 hours, technically there is no real need for
uptime limit other than to replenish loot, however this might change in
future if I add dynamic loot spawning. However, supply drops make
gameplay more interesting without the need for loot spawn replenishment.

Also, I will soon make server uptime a settings.cfg value.