Upgrade to Bootstrap 3

### Upgrade Mezzanine from Bootstrap 2.3.1 to Bootstrap 3.0.

This is still work in progress, I'm opening the ticket to track progress and receive feedback.

#### Current progress
- Sept. 25: Old static files have been swapped for the new ones. Base template, top, side and footer menus migrated to BS3.

#### TODO
- Blog
- Twitter
- Gallery
- Forms

#### Known issues
- Top menu displays dropdowns on click. This means that links with children won't take you to the linked page, just open the submenu. How should we proceed?