Add the possibility to select just one date and clic Apply in ranged mode

[lemonlab]

This code solve this issue :

• Click on one date
• Click Apply
  The date is not changed.

If you click again on the datepicker, select one date, click apply, and open again the datepicker : there is bigger problem : the calendar is empty.
This code solve those issues.

[Kichrum]

Here is a bug.

STR:

1. Open selector, choose any date and click "Cancel"
2. Open selector again and click "Apply". In console we'll see: "TypeError: Cannot read property 'clone' of null", window won't be closed.
3. Select any date, click "Apply"

Expected result:
Value should be set to clicked date.

Actual result:
The same as it was before: Invalid date, calendar is broken etc