Add tunnel_id support

Some logical ports may provide tunneling feature, in which the
networks will be isolated by tunnel_id.
Another use case we can utilize, is flow control as we do with
metadata.
Merge branch 'tunnel_id_support' of https://github.com/iHiroakiKawai/trema-edge into iHiroakiKawai-tunnel_id_support
add debugging information to datapath
- add dump_group_table()
Fixed an issue #84 of multiple actions in a bucket.
Change default OpenFlow TCP port to 6653
fixed the byte size of OFPXMT_OFB_PBB_ISID (issue #85)
- to 3-bytes from 4-bytes
update comment (issue #85)
Fix an issues that mutexes are not unlocked in error cases.
Fix an issues that mutexes are not unlocked in error cases.
rename openflow_event_handlers to openflow_switch_event_handlers
Merge remote-tracking branch 'origin/master'