[Feature Request] Manual control over dynamic playlists

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This came to me when I put on "Streets of London" by Ralph Mctell (One of the most recognized folk songs ever), only to be told I had no similar songs. Right well I DO, and I understand Last FM isn't perfect.
So I request a feature that allows me to choose a number of tracks which seed in the dynamic playlist, to help kickstart the "chain reaction". This is what I like most about Exaile, you can just stick a song on and it will play songs which are similar, forever.