nipet v2.2.0 stable

• add mmrprj.back_prj(div_sino=None) CUDA convenience
• add & expose projector sync=True CUDA optimisation
• add bprj(output=None) convenience (follow-up to #36, part of #33)
• remove unneeded aw2ali
• add mmraux.remgaps CuVec support
• clean .cuvec usages (AMYPAD/CuVec#17)
• use nimpa.dcm2nii
• drop PATHTOOLS & REGPATH (#40)
• support py3.10
• misc fixes
• misc tests updates