[isabelle-dev] Improved Graphview

[Makarius]

Attentive readers of incoming changesets might have noticed the recent 
improvements of the Graphview component, which was a not-quite-working 
student project from some years ago.

As of Isabelle/32b162d1d9b5 it is already quite usable, although a few 
details of the old graph browser are still missing.  I hope to wrap it up 
eventually for the coming release (this Spring) -- like various other 
things that are still in the pipeline and got delayed as usual (e.g. 
important reforms for Eisbach).


 	Makarius