geometry and pose

[simbamford]

geometry.py is a collection of small functions to do with geometry.

pose.py is a more principled attempt to apply batch operations to pose containers - it covers a lot of the same ground as geomtry.py.

Would be good to eliminate geomtry.py.

pose.py has several methods non-implemented. It has been suggested that it might be better (less work) to use the scipy.spatial.transform library and just wrap this where useful.