Previously, form and query parameters were handled together as
request parameters. Howeer, request parameters are a server-side
construct that's specific to the servlet specification. As such
they're not appropriate for the client-side documentation that
Spring REST Docs aims to produce.
This commit replaces support for documenting request parameters
with support for documenting query paramters found in the query
string of the request's URI and for documenting form parameters
found in the form URL encoded body of the request.
Closes gh-832