[z2107] Rewrite Checks required when entering a map

Expected way from now on is:
- Test if a map can be entered with Player::GetAreaTriggerLockStatus
- IF this doesn't return AREA_LOCKSTATUS_OK, and if wanted,
  send the fail-message with Player::SendTransferAbortedByLockStatus function.

Please feedback any hidden problems!

Signed-off-by: Schmoozerd <schmoozerd@scriptdev2.com>

(based on commit [12155] - 3d95311)

(based on commit [s1729] - d1828ad)
[z2108] Improve the RepopAtGraveyard handling of last commit. Thx to rsa for pointing

(based on commit [12156] - ccecf5b)

(based on commit [s1730] - f880c3b)
[z2109] Improve ObjectMgr::GetGoBackTrigger to get back to a trigger that actually ports into the map that could not be entered

(based on commit [12157] - 7dedd50)

(based on commit [s1731] - f002ef8)