- Bug: material emit was ignored (showed in preview render backdrop)
- Bug: world exposure was ignored
- Bug: lamp halo was ignoring 'render layer light override'.
Further reshuffled the way shadows are being pre-calculated, this to enable
more advanced (and faster) usage of Material lightgroups. Now shadows are
being cached in lamps, using a per-sample counter to check if a recalc is
needed. Will also work (later) for Raytracing node shaders.
- New: Material LightGroup option "Always", which always shades the lights
in the group, independent of visibility layer. (so it allows to move such
lights to hidden layer, not influencing anything).