[plt-scheme] Web Server Documentation Reorganization

The PLT Web Server manual was organized too much like a reference
manual with little guide to a user to understand how some modules fits
in to the big picture. I've reorganized the documentation with the
following paradigm:

--- Running the Web Server
--- Writing Servlets
--- Extending the Web Server

Other improvement related to this: I've added examples to almost every
servlet function. I have integrated the stateless and non-stateless
servlet documentation to put stateless servlets on a more secure
footing and make it clear that they are usable in real applications.
I've created an HTTP sub-module that encapsulates most of the HTTP
handling. (This will limit the need to use what used to be considered
internal Web Server functions.)

Jay

-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://jay.teammccarthy.org

"The glory of God is Intelligence" - D&C 93