Deprecate SampleRobot (#472)

Suggest TimedRobot as an alternative.

Remove -Werror from examples to avoid breaking build.

wpilibj/src/main/java/edu/wpi/first/wpilibj/SampleRobot.java

@@ -22,7 +22,13 @@ import edu.wpi.first.wpilibj.livewindow.LiveWindow;
  *
  * <p>Alternatively you can override the robotMain() method and manage all aspects of the robot
  * yourself.
+ *
+ * @deprecated WARNING: While it may look like a good choice to use for your code if you're
+ *     inexperienced, don't. Unless you know what you are doing, complex code will
+ *     be much more difficult under this system. Use TimedRobot or Command-Based
+ *     instead.
  */
+@Deprecated
 public class SampleRobot extends RobotBase {
 
   private boolean m_robotMainOverridden = true;