Navigation: Added support for authority-less URI schemes.

For URI schemes like "qrc:" (Qt resource) which do not include an
authority but only a path the method $.mobile.path.getLocation()
incorrectly returns a URL with a double slash after the scheme name.

In a Qt Webkit ThinClient application this resulted in continuously
adding up slashes in front of the path (e.g. "qrc://////index.html").

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Remark: Please note that I'm currently unable to test this modification (lack of a Qt ThinClient) and this change is untested in its current state. Just let me know whether you're able to reproduce and test or postpone this change until I'm able to do a final test myself.