Can run the default player from the menu

When the rundefault setting is enabled and no player
is running, the default player is displayed in the menu
with one button to run it.

If another player is running, the default player is not
shown.

Refs #84 #71
Display the rundefault setting for all positions

Refs #84 #71
Hide the indicator only if no player in the menu

Refs #84 #71
Show/Hide the menu, add the default player on setting change

Refs #84 #71
Remove the default player from the PlayerManager

Refs #84 #71
Don't create unnecessary separators

Also remove them when needed

Closes #114