Implementation of a ProjectionError for even grids, need discussion

Summary:
there are still some problems running e.g. 'test_till_random_material.py', I think we need this 'Valgrind debug'.
I just want to share the code with you in that way.

commented the ProjectioError to stop segmentation fault

Merge branch 'master' of ssh://c4science.ch/source/muSpectre into feat/ProjectionError_T1904

Merge branch 'feat/ProjectionError_T1904'

Test Plan: have some discussion and fix the Segmantation fault problem with 'test_till_random_material.py'

Reviewers: junge

Reviewed By: junge

Differential Revision: https://c4science.ch/D168