Add method to get the port number of a Joystick (#137)

wpilibj/src/athena/java/edu/wpi/first/wpilibj/Joystick.java

@@ -446,6 +446,15 @@ public class Joystick extends GenericHID {
     return m_ds.getJoystickName(m_port);
   }
 
+  /**
+   * Get the port number of the joystick.
+   *
+   * @return The port number of the joystick.
+   */
+  public int getPort() {
+    return m_port;
+  }
+
   /**
    * Set the rumble output for the joystick. The DS currently supports 2 rumble values, left rumble
    * and right rumble.