Add speed values to Player widget

[droumis]

Is your feature request related to a problem? Please describe.

When the - or + buttons to slow down or speed up the player are pressed, there's no display of what the speed increment has been changed to.

Describe the solution you'd like

Include speed values like 0.5, 1.5, 2.0, etc to the Player

Describe alternatives you've considered

1. Seeing how current values change might be an alternative (Add current value display to Player widget #229)
2. Use a discrete slider for speed instead of -, + buttons