Integrate Full Calendar into the UI

Integrate [fullcalendar.io](http://fullcalendar.io) into the UI

- Calendar shown in the main content container
- Add and Remove events through the sidebar (not hooked up to REST endpoints)
- Month, week and list view
- Design implementation according to latest wireframes and component PDF
- Fixed the position of the sidebar and header

TODO:
- Academic week number
- Changing terms
- Hook into REST endpoints when they're finished
- Popover with detailed information on hover of an event
- Sort out print view
I noticed there is some space between the buttons. Maybe we can float them, which will get rid of this horizontal space? If this is intended and the horizontal space is expected, never mind :D