[InstaGib] Add parameters for unlimited ammo, reloading time and for respawn weapon time

Add parameter for unlimited ammo in IstaGib mode, like in original. Parameter calling g_instagib_unlimited_ammo. Also, added checkbox in mutators in server create dialog, and condition when player dies, no pickup leaves from him (if unlimited ammo mode activated). In next commit I've added slider for changing weapon animation time, because default 0.3 is not the best time for InstaGib. In quake it's 2 seconds, in ut maybe less than 2 seconds, but also greater than 0.3. There is one event I've add - when client disconnects, animtime returns back after instagib. In this pull request I also pushing update in create server dialog - added slider for changing weapon respawn time.