Python API documentation generation tool Code

- Use different minimum graph sizes for latex & html output. These
sizes default to the values DotGraph.DEFAULT_LATEX_SIZE and
DotGraph.DEFAULT_HTML_SIZE, respectively. (This will make it easier
to add a command-line option to change those defaults.)

- DocstringLinker.url_for() is now an optional method

- Removed stale (unreachable) code

- DocstringLinker.url_for() is now an optional method

- DocstringLinker.url_for() is now an optional method

- Added max_width and max_height attributes to DotGraph -- if the graph
is larger than this, then it will be scaled down. Default value is
6 inches wide by 8 inches tall.

- Fixed bug in base style's def of EpydocProperty command

- Removed stale code that was accidentally not deleted in previous checkin

- Added some preliminary code for using dot2tex. This feature is not
yet working (and therefore disabled).

- Copy *all* of the epydoc builtin latex style files to the target
directory. This ensures that custom style files (which are now
copied to epydoc-custom.sty) can use \RequirePackage to extend any
of the builtin latex style files; and they can extend one another
as well.