The theme is download and applied in a separate thread.

Changed the SearchAndPersonaThread to include an instance of
SvxPersonalizationTabPage along with an instance of
SelectPersonaDialog. The constructor sets one of the instance and
the other one as null. In the execute() method, whichever instance
is null, the other one's process is done in the thread.

Change-Id: Iabfbdba63ce532ab794d3697977b6fab3fdaa832