[Suggestion] Use `Amber.Mpris` instead of `org.nemomobile.mpris` on newer SailfishOS releases

[Olf0]

A draft PR was posed in #34. For details, please see there.

Note that a code search for mpris reveals some more locations referring to mpris (the hits in extras/Lockscreen.qml can be ignored, see issue #102), which were not addressed in the draft PR #34. I.e. also in the file extras/main.qml and many more locations in qml/flowplayer.qml. But maybe these additional locations do not need to be addressed; I have not yet taken a closer look at them beyond finding them via GitHub's code search.