Full class hierarchy display

Migrated issue

Reported by: jhodgdon

On another issue, fgm mentioned the idea of having the API module create inheritance graphs, as is happening in a sandbox currently:
http://drupal.org/sandbox/fgm/1553284

As a note, the API module already parses/saves all the information necessary to create inheritance graphs. It's stored in the api_reference_storage table, and is being used to create the class hierarchies shown on class pages. If you go back a few versions (6.x-1.5 or so I think?), in fact, each class page used to show the entire class hierarchy for that class (now we only show direct ancestors, siblings, and children, not the entire family tree).

Anyway, we could definitely make a graph out of the information that we have. I haven't looked at the sandbox code yet, but the graph looks interesting...