OVSDriver: add skeleton for translating OF 1.3 set-field actions

This is hacky because loci does not yet support the set-field action.

I also added code for set-field vlan-vid, and IVS now passes the OFTest 1.3
actions.SetVlanVid testcase.
Merge into master from pull request #44:
OVSDriver: add skeleton for translating OF 1.3 set-field actions (https://github.com/floodlight/ivs/pull/44)