* Add a tool that automatically generates parts of a graphviz input from
an sql file
* Use that tool to generate bits of graphviz input from all the `create_` sql
files in `src/`
* Copy all those bits of graphviz input togeather to generate diagrams
for each table.
Added a dependency on "spp", simple preprocessor to do some
preprocessing around the templates. This will hopefully
allow the changes to be made in one place and propagate to
all the right pages.
Robin Malley