Repopulate button for dynamic playlist

[nobody]

It should be great to have a repopulate button, for the dynamic playlist, that add songs according to new song we manually add... e.g. if I add manually hardrock song, dynamic button add a few hardrock song, and keeps doing that until I quitt Listen. While playing hardrock song, i remove almost all those hardrock song (with the last one still playing) and manually add soft song, then click the button, and soft song from the library add itself, according to lastfm ratings...

The dynamic playlist in Amarok seems to be a reference to me :)

Keep up the great job!

[theli]

(In [910]) Fixes #192