Add automatic splitting of merged objects

[thraidh]

Many models are using merged meshes, that actually comprise multiple meshes which represent the base and moving parts. Those are represented as skinned meshes where the individual parts have different blend indices. Modders would usually export that merged mesh as an OBJ and painstakingly split the merged object into its parts by hoping to select the correct vertices and extract them into their own object. This tool should be able to handle that extraction process automatically. If a shape with SingleBlendWeights is detected, it can be converted into multiple OBJ groups/objects, so that all the triangles with vertices with blend index N form OBJ group $name-$N. This should probably be an option to turn on or off.

[Donkie]

sounds like a simple and nice feature!