Move vacc and lacc records into couch_mrview.hrl for use in chttpd
Allow couch_mrview_http to be more usable in chttpd

This makes a number of updates to useful utility functions in
couch_mrview, especially around parsing of requests, handling view
rows, and interacting with view source code. The `parse_qs` function
was updated to allow for parsing params from json bodies in addition
to just query strings.

The view_cb function is also updated to allow for reuse in chttpd, and
also for better flow control of when to start and complete chunked
responses, which is critical for multi view queries in COUCHDB-523.
Add mutli view query support

COUCHDB-523
Allow couch_mrview_show to be more fully utilized by chttpd_show