networking: add usage strings for subcommands

list, show and address commands now have its own help.
Merge pull request #38 from rnovacek/dev

networking: add usage strings for subcommands
Hardware: prettier output of chassis model when there's incomplete info
Hardware: added memory module information
Hardware: drop system subcommand and rename chassis to system

System subcommand displayed only hostname, which in case of hwinfo might be
pointless. After this patch, the hostname is displayed at the top of every
subcommand.

Chassis subcommand was renamed to system, because this name better represents
provided data - the data about "system", like the type (server, notebook), its
manufacturer and model.
Hardware: added motherboard subcommand

Motherboard subcommand displays model and manufacturer of motherboard.
Hardware: added support for disks
Hardware: cosmetic change in disks section
Hardware: cleaned after rebase
Hardware: cleaned after rebase v2

I forgot one thing and pushed the changes - hence the second commit.
Merge branch 'master' of https://github.com/pschiffe/openlmi-scripts