Locker/#54: Prevent screen locking while watching videos

Bug report from khorben on 07/03/2012 08:15:11
Some activities, such as watching fullscreen videos, should automatically prevent the screensaver from locking the screen.

This is also true for automatic hardware suspend (but may not apply here though).
Although not completely as good as hoped, the latest actions introduced (LOCKER_ACTION_ENABLE and LOCKER_ACTION_DISABLE) allow the screensaver to be disabled externally. It has to be enabled again manually afterwards.
The fix for bug #52 all helps for this issue, but does not fully solve it. It will have to be fixed otherwise.