Scale is negated in inverse bind matrices.
Vertex weights are normalized (glTF importer is limited to 4 weights per vert).
Fixed interpolation for animations where the first frame is not at 0.0.
Allows cached.dts version of assimp imported shapes to be loaded.
This commit deals with the problem that the keyframe timestamps are not standardized. Seconds, milliseconds and ticks are used depending on the import format. There is no metadata or property that specifies the format used, so the option is exposed to the user as part of the import options gui.
