Updated counter store for fewer string ops and therad local updates

...va/net/floodlightcontroller/core/internal/Controller.java

...n/java/net/floodlightcontroller/counter/CounterStore.java

src/main/java/net/floodlightcontroller/counter/ICounter.java

...et/floodlightcontroller/counter/ICounterStoreService.java

...va/net/floodlightcontroller/counter/NullCounterStore.java

...java/net/floodlightcontroller/routing/ForwardingBase.java

...et/floodlightcontroller/core/internal/ControllerTest.java