Imported NetworkAdapter UI module from nethserver-firewall-base package. Refs #2075
NetworkAdapter UI module: update-networks-db script must not be called by server-manager. Refs #2075
NetworkAdapter UI module: moved in Configuration category. Refs #2075
update-networks-db command: added license, reformatted.
update-networks-db: use udev function library to check filesystem is writeable. Refs #2075
Execute update-networks-db after udev-post startup and on udev events. Refs #2075