QUATERNION B_BONE_REST INVERT_VERTGROUP MULTIMODIFIER to the bpy armature modifier API. It also fixes a significant problem - In the docs, it refers to the 'VERTGROUP' field as being a string value, shared by lattice, armature, etc, referring to the 'VGroup' field in the armature modifier that defines a vertex group 'mask' which the armature's effect is restricted to. However, previously, for some very mistaken reason, in processing the getters/setters for the armature modifier, the VERTGROUP field was pointing to the quite different 'Vert. Groups' toggle in the armature modifier, that enables or disables using vertex groups for deformation (as opposed to envelopes). I've fixed this, so VERTGROUP points to the VGroup string, as is already defined in the docs and consistent with other modifiers like Lattice. A new field: 'VGROUPS' has been added, which is the analog to the 'Vert Groups' toggle.