(PUP-3644) Move urls to v3

This removes the "v1" HTTP API, which mounted
all of the various Puppet endpoints at "/" on the webserver.

In its place we now have the "v3" API, which includes
the versioned "/v3" prefix for all of the indirected URLs.
We still need to run down an answer as to whether we need to keep this around or not, but we can tackle that in a separate PR.