Add context managers for translations
Generalize transformations module to allow use without with statement, and to implement rotations.
Expand use of transformations to analysis submodules
Add information on transformation reverting to basic snapshot manipulation tutorial
Store simulation as weakref in transformations
Add unified syntax to decide whether to translate subsnap or entire snapshot in analysis.halo and analysis.angmom modules
Improve documentation for vel_center
Add null transformation
Fix null transformation
Rewrite virial_radius to use the new transformation paradigm
Add tests for halo centering, virial radius and diks alignment