Core/Scripts: Moved scripts from ScriptedGuardAI to guards.cpp
Core/Creature: Removed custom npcflags UNIT_NPC_FLAG_GUARD (now moved to flag_extras) and UNIT_NPC_FLAG_OUTDOORPVP (not used)
Thanks to Kaelima, Xanadu, Shauren and linencloth.
Signed-off-by: Manuel Carrasco <manue.l@live.com.ar>