Split animations into per action dae's with no meshes.

[dlannan]

The current animation export is messy and can be difficult to get right with multiple animations within a scene. The goal is:

• Output meshes individually. And identify animated meshes. These will be tagged as "Defold models" but still use a mesh buffer.
• Detect all animation actions and save them out as animation only dae files containing only the skeletons and the skins. No meshes.
• Export script info (into the meta data table) that allows easy access to available animations, and how to play them (maybe with correct timing and configs too).

Once complete, it should allow multiple animations in a scene to be easily exported to Defold and easily run in Defold.

[dlannan]

I have managed to do some of this work. Its a little more complicated than initially guessed. Will need to refactor some code to make this work well.

[dlannan]

Upodates to Defold have made this much better. A new mechanism will be added to extract anims separate from the mesh. It is more achievable now with the way the gltf export is working.