Factor the code for ".mode" out of do_meta_command() and into its own subroutine, to show how the new infrastructure makes this easy. We need to do the same for all the dot-commands. At the same time, add the -textjsonb option to .mode. (tags: qrf)

Factor the code for ".mode" out of do_meta_command() and into its own subroutine, to show how the new infrastructure makes this easy. We need to do the same for all the dot-commands. At the same time, add the -textjsonb option to .mode. (tags: qrf)