Update git source repos to https

* Now that edx-platform is fully open source, the right thing to do is
  have read-only http URLs be the default and get rid of all the
  nonsense ssh-oriented infrastructure for config/deployment.
* Also contains updates to edx-west/edxapp_prod.yml which make its
  behavior less mysterious. (but this isn't the important part)

@jarv does this look ok to you?