Add reader and writer for NXTomo files#939

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lauramurgatroyd wants to merge 12 commits intomasterfrom nxtomo-read-write

+786-1

Commits on Jul 26, 2021

Rename some attributes
lauramurgatroyd
committed

Commits on Aug 2, 2021

Generate file for test instead of downloading it
lauramurgatroyd
committed

Commits on Aug 3, 2021

Remove repeated code and rename filename to file_name
lauramurgatroyd
committed