newTranscript: do not reuse id

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Major refactoring of EditTrack.js.

New issues:
1. feature label is not displayed in edit track (intentional).
2. features jump up and down on edits (side effect of not reusing the same id)

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>