Check that conventionally constructed Blender skeletons work

[io7m]

There may still be issues with the way skeletons are exported.

The example stand_wave.blend skeleton has been constructed such that all bones are pointing "forward" (+Y) in Blender. This works correctly, but it's not how skeletons are usually constructed in Blender. Need to come up with some test cases to ensure that all skeletons work regardless of how they're constructed in Blender.

[io7m]

The attached "conventionally constructed" skeleton mostly works, but displays a bizarre
anomaly on the arm as shown in the attached video.

traditional.zip

8598d0cafb640d24992c83e7c31cadbdd8cd4452a39b77b1b0f9b0cf022a61c2 traditional.zip

[io7m]

It would be helpful if something in the example viewer would indicate when an animation has restarted. Possibly related to #9 as a notification would be a subset of the infrastructure required for #9.

[io7m]

Added a bug label, because there is one somewhere.

[io7m]

Could this anomaly be down to linearly interpolating quaternions rather than using spherical linear interpolation?

[io7m]

Yes, linear interpolation is the issue. Using spherical linear interpolation fixes the issue. Need to add an efficient implementation to jtensors.

See io7m-com/jtensors#11