Allow retrieval of raw request body

This adds connection.rawConnection.req.body which contains the fields from formidable.

The use case here is implementing a PATCH operation in a RESTful web service (PR for adding PATCH support to the web server is forthcoming :) )

connection.params contains additional parameters as well as the body from the request, all merged into one object. To get the original request body back you need to track and filter all the other parameters.