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).
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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.