Introduce new option -c[ompressvlans] to request
vlan ranges from kernel

(pls suggest better option names if this does not look ok)

$bridge vlan show
port	vlan ids
dummy0	 1 PVID Egress Untagged

dummy1	 1 PVID Egress Untagged
	 2
	 3
	 4
	 5
	 6
	 7
	 9
	 10
	 12

br0	 1 PVID Egress Untagged

$bridge help
Usage: bridge [ OPTIONS ] OBJECT { COMMAND | help }
where  OBJECT := { link | fdb | mdb | vlan | monitor }
       OPTIONS := { -V[ersion] | -s[tatistics] | -d[etails] |
                    -o[neline] | -t[imestamp] | -n[etns] name |
                    -c[ompressvlans] }
$bridge -c vlan show
port	vlan ids
dummy0	 1 PVID Egress Untagged

dummy1	 1 PVID Egress Untagged
	 2-7
	 9-10
	 12

br0	 1 PVID Egress Untagged
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>