populate clips' start and end attributes

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
have sendCommand return a promise

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
move removeClip to promises

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
move insertClip to promises

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
use media.start for sorting instead of refering to playlist

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
move medias time adjustment to it's own method in MeltedCollection

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
adjust times when melted is stopped as well

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
automatically add and remove medias from melted

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