(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.
Don't know if it matters, but the environment will serialize itself as a name string only.