Datepicker: Remove unwanted keyboard shortcut

Remove shortcut for closing the calendar and erasing the date (CTRL+END)
Datepicker: remove unneeded translation files
Datepicker: Make sure calendar sets new option value before datepicker
Datepicker: Make use of _getCreateOptions for min and max options
Datepicker: Use correct format for reading min and max options.

Use HTML5 date format for reading min and max attributes from input element.
Remove now unneeded helper method for parsing date strings.
Datepicker: Simplify usage of calendar options and avoid duplications