Refs #969 - Foreman-side changes for serving templates from the proxy

Needs the proxy-side PR to function.

This is a rebase of @GregSutcliffe's original https://github.com/theforeman/foreman/pull/751.
I think @GregSutcliffe is on a mission to get rid of most (if not all) fixtures usage, could you write a Factory for this and the other fixtures?