Created basic network graph objects, and implementation for the southbound API against the Ramcloud datastore

Change-Id: I2172dacb171f27ba2099ee5a52835030d2004689

Created basic objects and southbound API to build the network graph

Change-Id: I061efdf10e5e8549f7192844d10781dc28ee62d4

Added basic northbound get switch method on network graph

Change-Id: I4f2e4d4a4df00979abc927ef0772997dcdebc4e2
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/Link.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/Link.java
new file mode 100644
index 0000000..6c84382
--- /dev/null
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/Link.java
@@ -0,0 +1,17 @@
+package net.onrc.onos.ofcontroller.networkgraph;
+
+public interface Link {
+	public Port getSourcePort();
+	public Port getDestinationPort();
+	public Switch getSourceSwitch();
+	public Switch getDestinationSwitch();
+	
+	public long getLastSeenTime();
+	public int getCost();
+	
+	// Not sure if we want to expose these northbound
+	public long getSourceSwitchDpid();
+	public short getSourcePortNumber();
+	public long getDestinationSwitchDpid();
+	public short getDestinationPortNumber();
+}