Lightmass Override Volume

At the moment we can only place Importance Volumes which place Lighting Samples into that Volume.
However, in dense Areas (Houses for example) Lighting Samples may leak through thin walls. A Dark room next to a bright room separated through a thin wall causes the issue that characters are brighten near the wall in the dark room (or vice versa).

I suggest to implement a Lightmass Override Volume, which does what it says: It changes the Lightmass Settings locally within the volume.This way we can have separate Lighting Samples placements within the world and also decide which areas need high resolution lighting and which not