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

An update to @GregSutcliffe's original PR (https://github.com/theforeman/smart-proxy/pull/100/files). Ports his original feature to the new plugin api.
@dustints nice!

```
W, [2014-11-03T17:44:42.091978 #4895]  WARN -- : missing :foreman_url: from configurations. 'templates' module is disabled
W, [2014-11-03T17:44:42.092099 #4895]  WARN -- : missing :templates_url: from configurations. 'templates' module is disabled
```