[photran-dev] More docs updated

[Jeffrey Overbey <subscribe-photran-dev@xxxxxxxxxxxx>]

I updated the Developer's Guide as well.  I removed everything related 
to the parser and refactoring engine, since I am making some crazy 
changes to that, but the stuff that's left should all be accurate (esp. 
the list of plug-ins).

It is linked from the Contributor Info page on the web site.

(FYI we are going to have some new undergrads working on Photran who may 
find this useful.)

Jeff