add meta content manager section to engine admin

- add bootstrap formatting
- add acts_as_seo_content macro
- add resource retrviel helper for select tag
- add dummy articles scaffold
- add cascading dropdown menus for resource selection
- add validations to meta_contents
- HACK: :-( preload models for dev mode
- add after_destroy resource then destroy seo content
- add pending feature test to test meta content additions
- add resource_title helper to represent resources on the UI