This small addon adds the quest's level in front of it's name. Nothing more, nothing less.
This isn't done by replacing the whole functions of the quest log. Instead it intercepts the call of the function returning the quests name, level, ... It then prefixes the name with the level. That's all.
By doing so, it also works for the built in quest tracker.
Version 2.0 of the addon now also adds the quest's level to NPCs, but only if the level has been seen ingame before (I have to cache it since there is no way to get the level when talking to NPCs).