Implement individual operations on static and dhcp interfaces. Previously

Implement individual operations on static and dhcp interfaces. Previously
network interfaces could only be turned on and off as a group (all
static interfaces or all dhcp interfaces).

When used to start the interface a 'long form' ifconfig output is
used to show the status of the interface, but when stopping an interface
the script will simply output the name of the interface. This is simply my
personal preference. Hopefully as this functionality matures we can
stabilize on a prefered form of output for these scripts.

A stop command to the dhclient script now explicitly releases the dhcp lease.
Behaviour at system shutdown; however, is unchanged since dhclient is not,
by default, run at that time. The client will not release its lease
at shutdown.