shell, NM model: Use symbolic names for the DeviceType property.
shell: Allow embedding of onoffbox in clickable areas.

By preventing the click event from bubbling up.
shell: Factor out set_slave function.
shell: Move network interface information around on the page

The active state is now included with the settings, and the interface
hardware is described in a single row.  This is in preparation for
adding the slaves in a later commit.
shell: Show network slaves on their masters page.
shell: Omit active status for slave interfaces.

It mostly duplicates the information in the "Master" row.
shell: Bond slaves are "members", Bridge slaves are "ports".

Some are even Gold Members.
test: Adapt for previous changes.