Save meta title and meta desc on post save

Closes #4369
I may also have gotten carried away refactoring the editor-base-route mixin.
- Renamed `editor-route-base` -> `editor-base-route` to bring it in alignment with the view and controller mixins
- Consolidated editor route code into editor-base-route
- Removed `serialize` from EditorEditRoute, as it reimplemented the ember default

![save meta](https://cloud.githubusercontent.com/assets/1207005/4894781/f360bd5c-63d9-11e4-9f5b-9085fdeb51f4.gif)