[isabelle-dev] Improved Graphview

[Makarius]

Here is another small stepping stone: Isabelle/e82c72f3b227.  The 
Isabelle/Scala graph layout is now used to produce the session_graph.pdf 
for document preparation.  Moreover the same output is used for "theory 
dependencies" in HTML, and the old GraphBrowser applet has been 
discontinued.

What is still remaining is the "old browser" alternative of thy_deps, 
locale_deps, class_deps, thm_deps, code_deps.  It is not fully superseded 
by the new graphview yet, because the latter still lacks possibilities to 
fold subgraphs (according to hierarchical tree structure of the name 
space, or all preds/succs within the graph dependencies).


 	Makarius