Implementation of ScreenSwitchProvider

Implementation of ScreenSwitchProvider

This patch also moves responsibility of notifying Switch observers to base class SwitchProvider
and adds mechanism of timers depending on vconf configuration.

Values saved in vconf are:
    1. minimal time of interaction required to process switch
    2. interval between switch interactions
    3. auto repetition time

After acceptance of general idea suitable tests will be provided.

Change-Id: If7f92c442a3cc41e1019cd6e06555d8d0b3fc918