add vlan ethertype and fix pbb ethertype

For vlan header 0x8100 and 0x88a8 should be supported and
0x88e7 should be used for pbb by openflow specification.
0x9100, 0x9200 and 0x9300 is commonly used for vlan tpid.
Merge pull request #67 from iHiroakiKawai/vlan_tpid

add vlan ethertype and fix pbb ethertype