CORD-534 Added separate interfaces for Network and ServiceNetwork

Which are useful to implement OpenStack and XOS client implementation.
And removed "get" from get methods.

Change-Id: Icb477e48179a03e88003b1a38dd8f4ea83d92886
diff --git a/src/main/java/org/opencord/cordvtn/api/ServiceNetwork.java b/src/main/java/org/opencord/cordvtn/api/ServiceNetwork.java
index 6da6833..90de69c 100644
--- a/src/main/java/org/opencord/cordvtn/api/ServiceNetwork.java
+++ b/src/main/java/org/opencord/cordvtn/api/ServiceNetwork.java
@@ -24,7 +24,8 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
- * Representation of a service network.
+ * Representation of a service network which holds service specific information,
+ * like service type or dependency, in addition to the common network.
  */
 public class ServiceNetwork {