The vppctl was getting upset with large chunks of info generated
by repeated format() functions, so convert to use vlib_cli_output instead.
Also, refactor the show functionality into smaller functions,
separate from the input handling.
Change-Id: I5d0db5ac45ce4c1b59cd41526b837412e06b1ce0 Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>