Fix shell view for secgroup-* commands

Reasons:
 - currect code writes list of dict as they are,
   without any formatting, actually _print_
   method calls str() on each attribute,
   this issue spoils human-readable form of the shell output.

Changes:
 - updated "secgroup-list" (`rules` attributes was ignored);
 - updated "secgroup-show" (`rules` attribute was ripped off);
 - proposed new call "secgroup-list-rules <secgroup-id>";

Change-Id: Ic3f51b93af106c39de7eb3238f8bcffa3ea3cb95
Closes-Bug: #1300164
DocImpact: added new CLI command.
Merge "Fix shell view for secgroup-* commands"