base class hierarchy drawing could be improved

[prjemian]

discussed at today's NeXus telco (http://wiki.nexusformat.org/Telco_20160531)

"looks very complex, too many lines" - interpret this to mean too much overlap "idea is good for the manual but image is not yet ready" "in its current form: likely to create more questions than answers" "very informative for those who know NeXus" "very instructive to those learning NeXus" "note the recursion involving NXgeometry"

• [ ] try to spread this out: make drawing sheet larger?
• [ ] straighten lines
• [ ] automate .png file production
• [ ] consider alternative renderer for directed graph

[mkoennecke]

I printed it on A3 to see anything. I think the drawing could be improved by doing these things:

• Separate out those groups which can occur almost everywhere into a separate graph. I mean: NXlog, NXnote, NXcollection, NXgeometry etc
• Divide along the line of raw file format, processed data format