Added functionality to apply default themes.

* The themes are stored in the share folder under the personas directory
  in the gallery. The information is stored in a personas_list.txt which
  contains the info in the form headerFile;footerFile;textColor;AccentColor
  for the default themes.
* Changed the personalization_tab.ui to include _three_ buttons to show
  the default images.
* Changed the vcl/source/app/settings.cxx to read the persona information
  properly in the case of default personas.
* Some variable name changes.

Change-Id: Ib5f2167729a5fb7eb8061925679560accb934a44