Cleanup of event-history infra.

...va/net/floodlightcontroller/core/web/CoreWebRoutable.java

...troller/core/web/EventHistoryAttachmentPointResource.java

...ightcontroller/core/web/EventHistoryPacketInResource.java

...floodlightcontroller/core/web/JacksonCustomConverter.java

...erializers/EventHistoryAttachmentPointJSONSerializer.java

...e/web/serializers/EventHistoryBaseInfoJSONSerializer.java

...ontroller/core/web/serializers/OFMatchJSONSerializer.java

...tcontroller/devicemanager/internal/DeviceManagerImpl.java

...r/devicemanager/internal/EventHistoryAttachmentPoint.java

...main/java/net/floodlightcontroller/util/EventHistory.java

...a/net/floodlightcontroller/util/EventHistoryBaseInfo.java