Improvements to gstreamer backend.

- Use PlayBin instead of URIDecodeBin
- Change QUrl to QByteArray in pipeline
- Move URL stuff to FixupUrl() in GstEngine

src/engine/enginebase.h

@@ -34,6 +34,7 @@
 #include <QObject>
 #include <QUrl>
 #include <QVariant>
+#include <QByteArray>
 
 #include "enginetype.h"
 #include "engine_fwd.h"