Add a weekly view

It would be cool if a user could switch to a weekly display mode, which would display free/booked times like in outlook:

![wpf-scheduler-d](https://cloud.githubusercontent.com/assets/19407/16358117/586c1ae4-3b0a-11e6-90f6-432461d7959e.png)

A user can then determine when there are free slots to create a new event.
