Add previous and next year arrows from the days panel

![capture decran 2014-07-10 a 13 18 08](https://cloud.githubusercontent.com/assets/235510/3537678/eac0ed1e-0823-11e4-98b4-ad764f7ad4b6.png)

Exemple available at http://jsfiddle.net/bmichotte/tsEJ4/6/