sorry, large commit, but all changes are dependent:
Created a new plugin for the questsystem (called just "quest" for the moment because I'd had to rename the directory otherwise (the tolua script enforces this))
Added QuestPrereqs.h file and _QuestExport macro
Moved the GUI-name ↔ PlayerInfo map from QuestManager to GUIManager
Moved NotificationOverlay and NotificationQueue from overlays to quest and linked the overlays plugin into the quest plugin
Made QuestManager and NotificationManager ScopedSingletons with ScopeID GSLevel. Also removed both singletons from GSLevel and added the Scope instance instead.