Added boat location, and race start messages to the mock data interface

- Added proper support for signed and unsigned types. This includes automatic conversion to the correct data type (long to int, short, or byte).

- Moved code related to adding values into the byte buffer into the abstract Message class

Tags: #story[29]

src/test/java/seng302/server/TestHeader.java

@@ -0,0 +1,26 @@
+package seng302.server;
+
+import org.junit.Test;
+import seng302.server.messages.Header;
+import seng302.server.messages.MessageType;
+
+import static junit.framework.TestCase.assertTrue;
+
+/**
+ * Tests message header
+ */
+public class TestHeader {
+
+    @Test
+    public void testHeaderSizeEqualsActualSize(){
+        Header h = new Header(MessageType.DISPLAY_TEXT_MESSAGE, 1, (short) 1);
+        assertTrue(h.getSize() == h.getByteBuffer().array().length);
+
+    }
+
+    @Test
+    public void headerSizeIsSameAsSpec(){
+        Header h = new Header(MessageType.DISPLAY_TEXT_MESSAGE, 1, (short) 1);
+        assertTrue(h.getSize() == 15); // Spec specifies 15 bytes
+    }
+}