have the mongo driver filter out inexisting clips, and notify them

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
more natural arguments order

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
started playing message code

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
send 'started playing' message to caspa

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
send 'file not found' message to caspa

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