Actions in dataset builder

[laurencejackson]

Moves actions to the xnat_build_dataset function.

This is a much more flexible approach to creating a dataset from an xnat project.

• enables flattening the nested list with itertools
• enables actions to return multiple xnat objects
• more memory efficient when manipulating datasets

[github-actions[bot]]

Coverage Report

File	Stmts	Miss	Cover	Missing
mlops
Experiment.py	128	17	87%	36–41, 66, 68, 73, 111–112, 164, 194, 236–239, 243–244, 251–252
ProjectFile.py	27	1	96%	38
mlops/data/tools
tools.py	25	21	16%	13–50
mlops/data/transforms
LoadImageXNATd.py	35	24	31%	21–25, 46–84
TOTAL	240	63	74%

Tests	Skipped	Failures	Errors	Time
15	2 :zzz:	0 :x:	0 :fire:	1m 58s :stopwatch: