sugar for symbolic port and switch names #44

currently, we only support numeric OpenFlow port ID's and switch / data-plane ID's.

we can easily introduce tables like: portAlias(p.locSw, p.locPt, "gi0/0") and switchAlias(p.locSw, "core-router")

however, it would be nice if we also had sugar to support this. for example: p.locPt = gi0/0 and p.locSw = core-router. this issue is to track adding that sugar.