Ports Mind Procs from NT

ports some mind procs I made ages ago for NT

remove_X() procs remove the specified Antag, their Objectives and their Equipment
remove_all_antag() is for lazy people, might have like, 1 genuine use.
remove_objectives removes antag objectives.
remove_antag_equip() removes the special functions of PDAs and Radios.
wipe_memory() is just a shortcut to memory = null.

Testing: Been live on Artyom and NT for about 1 1/2 months with no issues.