(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.  Instead, the environment becomes a query
    parameter for GET requests, or part of the form body for POST
    requests.  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.