added absolute-minimum NeXus data file structure figure
Merge branch 'master' of https://github.com/nexusformat/communications
After many edits the documents hierarchy got out or order. Reordered it.
Minor edits on behalf of Bjoern Clausen
Minor edits -- HJB
Merge pull request #2 from jwuttke/master

Added postal code of Garching.
change "NXroot" to "root of HDF-5 file"
Clarify: base classes standardize the list and spelling of field names BUT other field names are allowed, even though they might not be recognized by other software
fixes #3
fixes #3
Merge branch 'master' of https://github.com/nexusformat/communications
remove
modify
remove
not "first" since we do not state a second necessity
clarify
redundant
avoids confusion with NeXus use of "entry"
NXcollection is a special case.  Out of place here, move further down.
Increase the emphasis on what is required and what is optional.