Add list natnets and natnetwork option

src/_virtualbox

@@ -21,14 +21,12 @@ _vboxmachines() {
 	done
 }
 
-# Get natnetworks
 _vboxnatnets() {
   vboxmanage list natnetworks | awk -F: '/NetworkName:/{print $2}'| while read natnet; do
     _wanted 'natnet' expl 'natnet' compadd $natnet
   done
 }
 
-
 # Roughly guess command options
 _vboxcommandoptions() {
 	cmd="$1"
@@ -135,6 +133,7 @@ _vboxmanage() {
 		'hostonlyif:change the IP configuration of a host-only network interface'
 		'dhcpserver:control the DHCP server that is built into VirtualBox'
 		'extpack:add or remove VirtualBox extension packs'
+		'natnetwork:add,modify,remove or start NatNetworks'
 	)
 
 	local context state line expl
@@ -151,7 +150,7 @@ _vboxmanage() {
 		list)
 			_arguments \
 				'--long' \
-				':list option:(vms runningvms ostypes hostdvds hostfloppies bridgedifs hostonlyifs dhcpservers hostinfo hostcpuids hddbackends hdds dvds floppies usbhost usbfilters systemproperties extpacks)'
+				':list option:(vms runningvms ostypes hostdvds hostfloppies bridgedifs hostonlyifs dhcpservers hostinfo hostcpuids hddbackends hdds dvds floppies usbhost usbfilters systemproperties natnetworks extpacks)'
 		;;
 		showvminfo)
 			_arguments \