[Bf-python] Mathutils::Euler and Math in the API-doc

[Anders Nilsson]

1) First I'd like to point out a problem with euler objects in
blender-python.

* Mathutil.Euler rotations are specified in degrees
* Objects rotation - obtained using getEuler() - is specified in radians
* IPO-tracks for rotation specifies euler angles as decadegrees (90
degrees=9 decadegrees)

This seems somewhat inconsistent to me. I know that the last thing is
due to historical reasons with the IPO-editor. The other two might be
natural given that Mathutil.Euler must be chosen such that it makes
sense for scripting and object.getEuler() can't be change or much code
would be broken. Still I see it as a problem.

2) Another thing is that almost none of the matrices provided in the API
are documented (what space? do they want post- och pre-multplication
with row or column-vectors?). What's up and what right, what coordinate
system are we in etc. Same goes for quats and especially the armatures.
I usually play around some until it works (tm) but that seems a bit
tricky.

What spaces what are defined in as well as armatures is the same for
python as it is for blender internal so perhaps some documentation that
is common to both? Perhaps it exists? Please enlighten me :)

Anders Nilsson (breakin)