Rearrange the automatic tests.

Split them into unit and integration tests.  Integration tests really
need to be run on the real platform (not in a VM etc) since they are
somewhat unstable or nonfunctional otherwise.

A few tests were previously broken by QUrl changes and they were repaired.
Removed one test since it was not providing a lot of value.

There are still a number of tests that rely on Q_AUTOTEST_EXPORT symbols.

Change-Id: Ic402abf0af946baa5945075d975b3f584f9ef280
Reviewed-by: Kalle Lehtonen <kalle.ju.lehtonen@nokia.com>

tests/auto/unit/qmediaimageviewer/images/invalid.png

@@ -0,0 +1,2 @@
+This is not really a PNG file.
+