v2.1 Uncompressed animation import support

Changelog:

• Added uncompressed animation support (import only for now)
• Added support for flagging additive animations
• Added frame counter to progress tracker in console (for imports only)
• Fixed issue where not already having an active action on skeleton would not allow you to actually select an action
• Fixed error importing single frame animations, 0 second duration
  • Also now set single frame animations to 0 second duration
• Add button to automatically set correct transform modes on custom or outdated skeletons
• Changed useless "loop check" option to "pad loop"
  • This imports the animation 3 times, setting the active frame range to the second loop. This is useful for things like non-linear interpolation or baking physics after the simulation has settled
• Added option to play animations from frame 0 during export
  • Useful for animations with frame range in middle of timeline, but still need simulations sampled from beginning of timeline
• Updated descriptions for improved clarity on what each option does
• Set all keyframe interpolation modes to 'LINEAR'

Notes:

• Uninstall previous versions of the add-on. Old versions had 3 separate add-ons for animation import, export, and skeleton export. All three should be uninstalled before installing this add-on.
• Restart Blender after installing this new version
• This add-on does not need to be extracted. The ZIP file should be installed as an add-on as-is.
• This add-on contains a DLL for compression and decompression, so it will only work on Windows.