Renamed networkgraph package to topology.
Moved NetworkGraphPublisher into new topology package.

net.onrc.onos.ofcontroller.networkgraph.* => net.onrc.onos.core.topology.*
net.onrc.onos.ofcontroller.floodlightlistener.NetworkGraphPublisher => net.onrc.onos.core.topology.NetworkGraphPublisher

Change-Id: I8b156d0fcbba520fee61e92ab659bb02cfa704ac
diff --git a/src/main/java/net/onrc/onos/core/topology/Path.java b/src/main/java/net/onrc/onos/core/topology/Path.java
new file mode 100644
index 0000000..1d15fc7
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/topology/Path.java
@@ -0,0 +1,24 @@
+package net.onrc.onos.core.topology;
+
+import java.util.Iterator;
+import java.util.LinkedList;
+
+/**
+ * Base class for Path representation
+ * @author Toshio Koide (t-koide@onlab.us)
+ */
+public class Path extends LinkedList<LinkEvent> {
+	private static final long serialVersionUID = 7127274096495173415L;
+
+	@Override
+	public String toString() {
+		StringBuilder builder = new StringBuilder();
+		Iterator<LinkEvent> i = this.iterator();
+		while (i.hasNext()) {
+			builder.append(i.next().toString());
+			if (i.hasNext())
+				builder.append(", ");
+		}
+		return builder.toString();
+	}
+}