Blender Git Loki

Refactor Collada: Major rewrite of the AnimationExporter

* Mostly reorganized the classes and made them more readable.
* The animation sampler now can be used for any animation curve.
Before the sampler only looked at curves which are supported by
Standard Collada 1.4. However the Collada exporter currently
ignores all animation curves which are not covered by the 1.4.1
Collada Standards. There is still some room for improvements
here (work in progres)
* Removed some unnecessary dependencies and cleaned up many
functions which have become unnecessary and no longer used.
* moved functions between classes to better match the class
responsibilities.
* took care that the functions are kept small and understandable
* removed intermediate structures which are no longer needed
* cleanly separated the Animation sample part from the
Collada part so that they can be treated independently from each
other

Known issues:

* Some exports do currently not work reliably, among those
are the camera animations, material animations and light animations
those animations will be added back next (work in progres)

* Exporting animation curves with keyframes (and tangents)
sometimes results in odd curves (when parent inverse matrix is involved)
This needs to be checked in more depth.

* Export of "all animations in scene" is disabled because the
Collada Importer can not handle this reliably at the
moment (work in progres).