First steps towards suggestions.

Tackling video suggestions first, since they seem the highest leverage for the site.

Suggestion model: Intended to be a generic storage object for suggestions about anything.

Todo:
- Suggestion accepter classes, that consume a Suggestion and apply it to the appropriate model.
- Suggestion validation: don't accept suggestions for things we already know
Adds admin review tool for Suggestions.

Reworked some of how we store data to allow for negative reviews

Todo
- Write class to actually accept suggestions
Allow accepting suggestions.
Test for MatchSuggestionAccepter.
Change button color for suggestions.
Improvements to the flow for suggesting videos.

- Admin pages have thumbnail video previews.
- Redirect users to the same page after logging in
- Log out links for admins and users
- Slightly bigger labels in admin tool
- Easier youtube video searching buttons for adding page
Improvements to the styling of the pending suggestions.
Fix problem when not accepting any suggestions.
Display success banner on video suggestion.