Clean up of the DatePicker

1. Removed a duplicate DatePicker stylable.

2. Fixed a bug that if the user wrongly desires to have the
   calendar view and spinners hidden despite that DataPicker
   ovrrides such incorrect choice to show at least the spinners
   the min adn max date attributes are igonored.

Change-Id: I6307db71aca837ad790aea59fa70ead393feb066