PHP 5.5.9+ adds the new static `class` property which provides the fully qualified class name. This is preferred over using class name strings as these references are checked by the parser.
* Fix auto-increment not updating
This is due to the addition of caching for settings. If we're not
explicitly saving the Settings model, then the cache isn't getting
updated, causing the asset tag auto-increment to get an old cached
version with the wrong number
* Move Setting cache clear to an observer
