Bureau structure page

- Add bureau structure page contents.
- Add content slider functionality for mobile org chart.
- Add jump-link__back & jump-link__bg modifiers.
I agree -- I pretty much put these styles here for lack of a better place. It's fairly specific behavior, so I wasn't sure if it made sense to create a more generalized class until the pattern shows up somewhere else. Maybe it could be broken out into some separate classes -- `link-border`, etc?