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/cpp/IterativeRobot.cpp

@@ -30,7 +30,13 @@ void IterativeRobot::StartCompetition() {
   while (true) {
     // Wait for driver station data so the loop doesn't hog the CPU
     DriverStation::GetInstance().WaitForData();
+    if (m_exit) break;
 
     LoopFunc();
   }
 }
+
+void IterativeRobot::EndCompetition() {
+  m_exit = true;
+  DriverStation::GetInstance().WakeupWaitForData();
+}