Add the datepicker layout

[Z7oussem]

Description

Add the datepicker layout

Modifications

1. Add new @datepicker annotation
2. Implement the DatePickerGenerator
3. Improve the demo app to support the datepicker layout
4. Add the datepicker add on

Expected behavior: Support the datepicker layout

[SaifJerbi]

It's fixed by adding new external project https://github.com/JsonSchema-JavaUI/sf-java-ui-addons
Implementing a mechanism to support external librairy addons