new sequence: display tracks in timeline window for source clips when loaded in the source monitor

currently when creating a new sequence if you load a source into the source monitor, the available audio and video tracks are not displayed. So if you cut the clip into the timeline, currently you have to go back and delete the audio or video channels you don't want. Kind of ridiculous.

Would make more sense if the tracks were visible in the timeline window so you can select them before doing the first edit... as they are after the first edit so you can select which tracks you want or don't want.

See Avid Media Composer as example.