added getId to address interface, closes mitreid-connect#958

Author: jricher

openid-connect-common/src/main/java/org/mitre/openid/connect/model/Address.java

@@ -20,6 +20,12 @@
 
 public interface Address extends Serializable {
 
+/**
+ * Get the system-specific ID of the Address object
+ * @return
+ */
+public Long getId();
+
 /**
  * @return the formatted address
  */