Scripts/FollowerAI: Some cleanup:

- FollowerAI properly resumes follow after evading.
- Removed duplicated getters from CreatureAI (IsEscorted vs IsEscortNPC), they were used to do the same thing
- FollowerAI properly assists in combat.
- FollowerAI properly despawns if quest is abandoned.
- FollowerAI now supports dynamic respawning for escort NPCs.

sql/updates/world/3.3.5/2019_08_01_00_world.sql

@@ -0,0 +1,4 @@
+-- 
+DELETE FROM `spawn_group` WHERE `spawnType`=0 AND `spawnId` IN (22831,36626,23708,39059);
+INSERT INTO `spawn_group` (`groupId`,`spawnType`,`spawnId`) VALUES
+(3,0,22831), (3,0,36626), (3,0,23708), (3,0,39059);