(PUP-3642) Remove environment name from URL path

This commit makes some changes to the indirector network layer
such that the environment name is no longer a part of the main
URL path structure.  This will allow us to have a more finite URL space
and run Puppet in the same webserver with other apps, without
worrying about URL collisions.  Instead, the environment becomes a query
parameter.
@joshcooper so the distinction you're getting at is data that is known to be www-form-urlencoded?  Since we know that in the case of our POST requests they are always using that content type?  Because if there were any other Content-Type for our POST requests, we'd have the same problem that we currently have with PUT requests, unless we put the environment into the query string... right?