Add ability to end startCompetition() main loop (#2032)

This is useful for both cleanly exiting from simulation and for unit testing
at a framework level.

This change required removing move constructor/assignment from IterativeRobot.

wpilibc/src/main/native/include/frc/TimedRobot.h

@@ -34,6 +34,11 @@ class TimedRobot : public IterativeRobotBase, public ErrorBase {
    */
   void StartCompetition() override;
 
+  /**
+   * Ends the main loop in StartCompetition().
+   */
+  void EndCompetition() override;
+
   /**
    * Get the time period between calls to Periodic() functions.
    */