rollback to h5py 2.x

See merge request !34

This reverts commit 17726427.

Conflicts:
	nxtomomill/settings.py

[utils][change_image_key_control] filter frame indexes to insure they are contained in the image_keys buffer

fix relative path

Closes #24

See merge request !33

[converter][tomoh52nx] remove magnified pixel size

Closes #20

See merge request !31

- only write pixel size. A path can still be provided by the user. Otherwise we will try the following path to get the pixel size to be store in the NXTomo (with this order):

"technique/optic/sample_pixel_size ",
"technique/optic/sample_pixel_size",
"technique/detector/pixel_size"

/close #20

Better management of file

Closes #17

See merge request !30

- if this is the case ask user for a confirmation because this is probably not the file he wants to translate.

/close #17