Blender Git Loki

Yet another fix for node groups localization: The ntreeLocalMerge function can not be used to free localized node groups, because it is not commonly called to free the localized node trees. Instead these
data blocks are freed using the standard ntreeFreeTree function, so freeing localized node groups has to be done there. This means an ugly loop over G.main to detect localized groups, but should not be a
big problem in practice.