Blender Git Loki

fix [#25429] Armature modifier and inverted vertex group
- the invert flag was only being used for multi-modifier, but there is no reason not to use this in normal cases as well.
- Armature modifier RNA name 'vertex_group' was incorrectly named 'vertex_group_multi_modifier' (own fault), confusion was caused by 'invert_vertex_group_multi_modifier' which was correct.