Display all pda-risc node labels as left-aligned
Add global node and edge attributes and fix indentation

Now `set-global-node-attribute' and `set-global-edge-attribute' can be used to
set global node or edge attributes applicable to all nodes and edges in the
given graph. They compile into

  node [ ... ];

and

  edge [ ... ];

respectively.

Additionally, I fixed some problems with proper indentation of subforms and a
bug where subgraphs were using the keyword "digraph".
Clean up implementation of `dot-graph-data.rkt'
Remove unnecessary type variable
Prevent make-dot-graph from showing visual noise (i.e. blocks)

I also added some more informative commenting.
Default to monospace fonts and provide a hook for 8.5x11 paper graphs
labels are also visual noise
Rearrange and add some comments
rearrange valid-term?, shorten, and textify
Add documentation to add-term-node
rearrange again
Give pop and push nodes distinctive visual features
Abstract to and provide uid->node-name
Provide a summaries set as UIDs
New procedures to add summary and push-pop-web edges to digraphs
I need to think about valid-term? more

The trouble is I need to bridge the gap over these useless terms.

I should probably have a pass that deletes all these useless control nodes now
that we have succs and preds.
fix typos in annotate-dot-graph
webs go both ways
Prevent web edges from affecting layout of graph
Add coloring of push-pop-webs