Resolve "Remove strawberrymusicplayer from the repo"

Strawberry player is present upstream and the package is well-maintained. It will be the latest version once we perform a merge from upstream.

I also replaced "Music music player" with "Strawberry music player" in generic name of px-music-player, keeping "Music" for the desktop icon and such.

Was:

Name=Music
GenericName=Music Music Player

Now:

Name=Music
GenericName=Strawberry Music Player

I also edited it to preserve original build phases that seem to be essential to keep (such as wrap-program and tests)

Closes #279