Create Save algorithm to create NXTomo file.

[mantid-builder]

Original Reporter: John Hill

This ticket is blocks : TRAC11041

Create a save algorithm to output NXTomo nexus files.
http://download.nexusformat.org/sphinx/classes/applications/NXtomo.html

Testing:
Use load FITS algorithm with files from [10061].
Use SaveNXTomo algorithm to create a .nxs file.
Check that the file can be loaded (Preferably with DAWN [http://www.dawnsci.org/] which shows the images under entry1/tomo_entry/data/data, or using HDFView and check the data matrix is populated)

[mantid-builder]

This issue was originally trac ticket 10194