pieces now come from a different mongo collection

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
fps now is in piece.video, not directly under piece

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
don't use Date

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
use $ instead of - for playlist/clip id separators in filename

Signed-off-by: Tomas Neme <lacrymology@gmail.com>