Added MessageDecoder interface. All decoder implement this.

Added DecoderFactory. This creates an appropriate decoder based on a MessageType.
BoatActionDecoder implements MessageDecoder.
BoatLocationDecoder implements MessageDecoder.
HeartBeatDecoder implements MessageDecoder.
JoinAcceptance implements MessageDecoder.
RaceStatusDecoder implements MessageDecoder.
RequestToJoinDecoder implements MessageDecoder.
XMLMessageDecoder implements MessageDecoder.
Refactored CourseWind decoder/encoder. CourseWind decoder/encoder is for an individual CourseWind.
CourseWinds decoder/encoder is for the combined message from the API.
Documented BoatAction, and it now contains a BoatActionEnum instead of a byte.
Refactored CourseWind and CourseWinds classes. They now expose correct units, instead of packed units.
Added CourseWindDecoderTest, and updated CourseWindsDecoderTest.
issue #35 #36
#story[1095]

racevisionGame/src/test/java/network/MessageDecoders/RequestToJoinDecoderTest.java

@@ -28,7 +28,8 @@ public class RequestToJoinDecoderTest {
         byte [] testEncodedMessage = RaceVisionByteEncoder.encode(message);
 
         //Decode.
-        RequestToJoinDecoder testDecoder = new RequestToJoinDecoder(testEncodedMessage);
+        RequestToJoinDecoder testDecoder = new RequestToJoinDecoder();
+        testDecoder.decode(testEncodedMessage);
         RequestToJoin decodedMessage = testDecoder.getMessage();
 
         return decodedMessage;