Create RecA_v1.2.java

Minor modifications : based on earlier meeting have added method to implement from app to check extra edge presence. getTail() method can be used to return set of Tail nodeconnectors. Also link changes as polled by RecA are sent to Master over TCP using SendtoMaster function. @Avinash - had a doubt here. Do I have to explicitly specify the edge that has come up/gone down -> presently just sending linkup linkdown. However modification on RecA will have to be done to ensure LXB takes care of corner cases such as when switch is handed over to alternate network and multiple inter-AS paths exist. 

Note : define the Set of tail node connectors as under:
new HashSet<NodeConnector>();