Create HeaderFieldsException.java

Support for IPv6

src/main/java/net/floodlightcontroller/staticflowentry/HeaderFieldsException.java

+package net.floodlightcontroller.staticflowentry;
+
+public class HeaderFieldsException extends Exception {
+
+	/**
+	 * 
+	 */
+	private static final long serialVersionUID = 1L;
+	
+	 public HeaderFieldsException(String s) {
+	      super(s);
+	   }	
+
+}