[Owncloud] Switching to PHPUnit

[Robin Appelman]

Currently we use SimpleTest for out unit tests inside ownCloud, while this 
works fine for basic usage from the browser or the ci server, it lacks the tool 
support that phpunit has.

I've done most of the work of switching to phpunit in the phpunit branch and 
I'm planning to merge it after the release.

Currently the main work of the migration is done using a small compatibility 
layer for SimpleTest on top of phpunit, this is sufficient at the moment but in 
the long run the test cases should be converted to phpunit properly.

 - Robin Appelman