z_stitching: pylint errors

pylint gives the following errors for the stitching volume:

************* Module nabu.stitching.frame_composition
nabu/stitching/frame_composition.py:151:4: E0213: Method should have "self" as first argument (no-self-argument)
************* Module nabu.stitching.z_stitching
nabu/stitching/z_stitching.py:678:44: E1123: Unexpected keyword argument 'end' in function call (unexpected-keyword-arg)
nabu/stitching/z_stitching.py:678:44: E1120: No value for argument 'stop' in function call (no-value-for-parameter)
nabu/stitching/z_stitching.py:733:8: E1205: Too many arguments for logging format string (logging-too-many-args)
nabu/stitching/z_stitching.py:867:31: E0601: Using variable 'proj_0' before assignment (used-before-assignment)

Related: !223 (merged)