Moving logic from `LinkingFunction` to `controller`.

Everybody, I'm quite new to AngularJS so I think there is a lot to tell about my work… At least, I ensure tests stay green :)

My original need is to use the Datepicker component but make it able to render days where there is planned day. I started to extend it by creating a new directive with the same name. But I needed to access to some function, as `refill` to call a function of mine which bind days to their respective events and set a class to the related days.

As `refill` was is in the `LinkingFunction`, I could not access it through my own `LinkingFunction`.

Here is my PR to allow people to extend the component default behavior.

Please criticize, please be gentlemen!