Datepicker: Introduce value option

Change status caching, fix existing value related methods, introduce
$.date construction with date object, selected property is null by
default, add selected getter
Calendar: Add calendar widget

Add calendar widget by copying and renaming datepicker widget files.
Remove datepicker functionality, options and methods from Calendar.
Remove calendar functionality, options and methods from Datepicker.
Adjust tests due to split and changed specification. Remove duplicated
demo files and fix some demos. Simplify calendar generation, use CSS
instead of inline styles. Fix destroy method. Make use of uniqueId
method. Fix focus highlighting when month is changed. Add version
property. Add common unit tests. Fix input keyboard handling.
Calendar: Add min and max option.

Improve render day cell mechanism.
Calendar: Remove select callback reference
Datepicker: Code clean up for events
Datepicker: Remove unwanted keyboard shortcut

Remove shortcut for closing the calendar and erasing the date (CTRL+END)
Datepicker: Simplify usage of calendar options and avoid duplications
Datepicker tests: Add open and close unit tests
Datepicker: Improve document click event
Calendar: Fix broken day table cell attributes
Datepicker tests: Rewrite event unit tests
Calendar: Fix multiple calendar styles
Calendar: Fix German localization
Datepicker: Fix localization demo
Datepicker: Several minor code improvements

Several minor code improvements and make suppressExpandOnFocus
an internal variable
Calendar: Fix hover event setting and removing
Calendar: Improve code style and clean up
Calendar: Focus class is not removed when using arrow keys
Datepicker: Remove unwanted CTRL+HOME shortcut
Datepicker: Remove support for enter key on input