update invariant checks to match the new topology interface
Fix bug in mesh topology factory

It was creating links in one direction but not the other
Make sure switch DPID is read as integer
Add code to parse ovs-ofctl flows-dump into pox table
Read flow table from TestONOVSSwitches
Add simpler tracker of connected pairs as result of policy change
Update connected pairs tracker on AddIntent/Remove intent
Handle special case when all controller are dead! when adding intents
Print invariant name on violations
update invariant checker to match new topology interface
consider connected pairs on checking connectivity