- now we will first try to get the camera using NX_class == 'NXdetector' from the instrument group
- if fails then we try to retrieve group that looks like detector (containing `data` dataset which should be 3D)
- users can still force camera names. Either from settings.py of from command line parameter '--valid_camera_names'

Include utils to mock bliss scan from tomwer

- get_nx_detectors: retrieve detector nodes from NX_class
- get_nx_detectors: retrieve detector from structure: should contain a dataset named 'data' with 3D shape

Several minor fix

See merge request !36

- if true then raises ValueError if cannot reach some requested data
- if false the set a default value and add a warning message to logs

rollback to h5py 2.x

See merge request !34

This reverts commit 17726427.

Conflicts:
	nxtomomill/settings.py