daemon: Add NetdevMonitor

This is a MultiResourceMonitor for network interfaces.

Signed-off-by: Stef Walter <stefw@redhat.com>
 * Removed debugging code
 * Fixed theoretical buffer overflow
web: Factor cgroup plot setup out of DockerClient

We'll use this for services also.

Reviewed-by: Stef Walter <stefw@redhat.com>
web, NM model: Expose numeric State codes as well

Reviewed-by: Stef Walter <stefw@redhat.com>
web: Add graphs to networking page

Fixes #454
Reviewed-by: Stef Walter <stefw@redhat.com>
web: Add graphs to network interface page

Fixes #457
Reviewed-by: Stef Walter <stefw@redhat.com>
web: Remove network-traffic-status page

Closes #728
Reviewed-by: Stef Walter <stefw@redhat.com>