Cleaned medical items code, +new items +defenses

Added new item "Doctor's Bag" which replaces the item Briefcase (which
didn't have much of a use) craftable with bandage+medkit, yeilds 70
health points.

All medical items such as medkits, bandages, doctor bag now run on the
same code.

New explosive craftables: Motion Mine and Phone Bomb.
Motion mine acts just like a cap mine used to, if picked up while armed
it will explode. New functionality allows arming while inside a trunk,
bag or box to set traps.
Phone bomb can be used to remotely kill players, two phones are needed,
one on the bomb and one to trigger it.

Defenses code added and mostly completed, explosives will call
CreateStructuralExplosion which will damage defenses. Defense items can
be built into permanent objects wither with hammer or screwdriver, which
will result in the object being flat or upright respectively.