Add new scene controller with touch display example.

Upgraded RF24 to latest version which supports SoftSPI. 
Added DigitalIO and UTFT libraries to support the new example.
Fix problem reported in RelayWithButtonActuator example.

libraries/DigitalIO/examples/PinIOConfigToggle/PinIOConfigToggle.ino

@@ -0,0 +1,16 @@
+// Test the config() and toggle() functions.
+#include <DigitalIO.h>
+
+// Set runtime pin number.
+PinIO pin13(13);
+
+void setup() {
+  // set mode to OUTPUT and level LOW
+  pin13.config(OUTPUT, LOW);
+}
+void loop() {
+  pin13.toggle();
+  delay(100);
+  pin13.toggle();
+  delay(400);
+}