disable double-axis on master branch
generic update
update TODO
contrast inversion now works also with short option
Add shifts and new convenience functions

* Add shift_[xyz] for volume and shift_[xy] for detector
  together with parameter handling in the respective functions

* New functions to apply parameters to a volume or a projection image
add gfunc3_set_x0 function
fix bad sign in compute_rotate_basis
reassign shape in gfunc3_read_from_stack since rotation can change it
introduce shifts into image_rotation and xray_backprojection_sax
add shifts to template file
Reorder functions to avoid step artefacts

* Normalize first to have zero background for rotation and zero-padding

* Use convenience functions to apply reco parameters to volume and images