Previously it wasn't possible to select a set of dates with a shift click, now we can.
This works only when the mode CPRangeDateMode is set.
It has the same behavior as in Cocoa.
Previously the showcase of Aristo and Aristo2 didn't work because several bugs in the class CPDatePicker.
This PR fixes these problems :
- The first problem was when displaying a textual datePicker, the class tried to calculate different things for the calendar (good optimization as well).
- The second problem was about the calendar and the hands. It wasn't possible to display a PatternColor made with an image in a layer, now we use a PatternImage and the method CGContextDrawImage to draw the hands.