fixes #812 - new permissions model, user group role and nest support, role filters for better granularity

Contributions from:
* Daniel Lobato <elobatocs@gmail.com>
* Joseph Magen <jmagen@redhat.com>
* Tom McKay <thomasmckay@redhat.com>
* Greg Sutcliffe <gsutclif@redhat.com>
* Dominic Cleal <dcleal@redhat.com>
i18n - extracting new, updating rails, pulling from tx
Fixes #4536 - store fix_db_cache setting values correctly as YAML
Fixes #4226: add a Rake task for plugins that compiles their assets into core assets pipeline
fixes #4524 - The logged in user should be the default one in create new hosts