[10299] Add new script call ProcessEventId

Let script library know when some event is about to start. Event id's may be found in several sources, such as spells, GO's and transport/taxi paths.
Database scripts may be prevented by returning true from script side whenever needed. If false, DB script will run like normal.
New database table event_id_scripts will need a ScriptName for the event id, in same way as for example areatrigger_scripts.

Signed-off-by: NoFantasy <nofantasy@nf.no>

src/game/World.cpp

@@ -1087,6 +1087,9 @@ void World::SetInitialWorldSettings()
     sLog.outString( "Loading AreaTrigger script names..." );
     sObjectMgr.LoadAreaTriggerScripts();
 
+    sLog.outString( "Loading event id script names..." );
+    sObjectMgr.LoadEventIdScripts();
+
     sLog.outString( "Loading Graveyard-zone links...");
     sObjectMgr.LoadGraveyardZones();