Get rid of old minion proxy code in favor of new, better proxy code

Now minions and services use the same proxy.

Changes:

What used to be ```/proxy/minion/minion_name``` is now ```/api/v1beta1/proxy/minions/fully_qualified_minion_name```.
It might make sense to omit the scheme here and let the proxying code figure that out. I'll make a change.