add repeat-single button to toolbar
Sometimes you do not only wish to repeat a whole album, you may wish to endless listen to your very favourite song. This MR adds a repeat-single button to the toolbar to allow exactly this.
Pressing the button will turn off the repeat-album and enable the repeat-single since media player's playbackMode can have only one value set.
Here a screenshot for the visual part (E5 = smaller screen, left margin is better on e.g. Xperia X):