commander: reboot/shutdown usability fixes

- always check with state machine before reboot/shutdown
 - respect BOARD_HAS_POWER_CONTROL (shutdown from command, low battery, power button)
 - px4_shutdown_request add optional delay and always execute from HPWORK
 - px4_shutdown_request split out px4_reboot_request

src/modules/replay/Replay.cpp

@@ -852,7 +852,7 @@ Replay::run()
 
 		//TODO: add parameter -q?
 		replay_file.close();
-		px4_shutdown_request(false, false);
+		px4_shutdown_request();
 	}
 
 	onExitMainLoop();