Power plugin test suite

[Bastien Nocera <hadess hadess net>]

Heya,

We now have a test suite for the power plugin in gnome-settings-daemon,
thanks to Martin Pitt's work.

Any changes to the power plugin will now require a test case, or
adapting existing test cases. Obviously, no breaking the test suite
either :)

On Fedora, make sure python-dbusmock 0.3.1 is installed, and run "make
check" in the root directory.

Cheers