Fix some audio cd related issue: not playing, skipping tracks with gstreamer, no length shown

Don't start a new track in the EngineController if the new title is the one we just started. (fixes bug 222405)
Handle a device specifier (?device=<deviceName>) in EngineController::playUrl, the old code would not play if the deviceName had a slash (/) in it. (fixes bug 261175).
Use KIO:NetAccess::stat to compute track lengths, previously shown as 0:00, fixes bug 207806.
src/core-impl/meta/cdda/AudioCdTrackProvider_p.cpp (AudioCdTrackProvider::Private::Private,AudioCdTrackProvider::Private::deviceAdded): Fix some typos, that may have caused crashes.

Courtesy: Arnold Metselaar