Complete Rework of Gun code

- Reworked the way guns work, splitting ammo_storage into 3 types with their own details. Empty_magazine is gone, and automatics now properly accept and remove magazines
- Automatics have a new verb : toggle burstfire. Burst fire makes you fire a lot of bullets at once, but with a long cool-down
- Added a box of flares to let you carry a few around. Spawns in emergency toolboxes if a flashlight doesn't
- Shotguns now eject empty shells, which can be used to make new shells
- Attempting to load a gun from an ammo box now requires you to stand still or else you don't load anything and you drop some bullets
- Added a speedloader for the traitor revolver for balance purposes (get it by ordering the 2-tele ammo box)
- Added an ammo box for the detective, and his locker now has 1 loader & 2 ammo boxes (for balance purposes)
- ammo_storage now functions on a modulo system:  you can set the intervals at which a sprite changes. Empty sprites for non-empty mags are automatically changed to the next-lowest version
- Should fix  #1385
*Should be ready to go now