Retire canned resp append checkbox on ticket reply

The default mode going forward will be to insert when Rich Text support is
enabled and append otherwise. To clear the draft the user can simply click
reset or delete draft icon on the bar.

Enable delete draft option on reply & internal note boxes for consistency.
Merge pull request #973 from protich/feature/retire-cannedresp-append

Retire canned response append checkbox on ticket reply.

Reviewed-By: Jared Hancock <jared@osticket.com>