ddb: Add CSV option, sorting to 'show (malloc|uma)'

Add /i option for machine-parseable CSV output. This allows ready copy/
pasting into more sophisticated tooling outside of DDB.

Add total zone size ("Memory Use") as a new column for UMA.

For both, sort the displayed list on size (print the largest zones/types
first). This is handy for quickly diagnosing "where has my memory gone?" at
a high level.

Submitted by: Emily Pettigrew <Emily.Pettigrew AT isilon.com> (earlier version)
Sponsored by: Dell EMC Isilon