AI server: more code cleanup
AI server: room statuses are no longer magic numbers for clarity.
foreach_stlmap() now handles locking the map implicitly; implmented foreach_stlmap_nolock() to behave otherwise. Removed all code that handled manually locking the STL container's lock.
AI server: removed CNpc::m_byGroup in favour of Unit::m_bNation. Implemented temporary CUser::GetNation() getter and cleaned up all uses.
AI server: Implements CUser::GetLevel() & CNpc uses Unit::m_bLevel instead of CNpc::m_proto::m_sLevel.