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/testPinIO/testPinIO.ino

@@ -0,0 +1,19 @@
+// Scope test for PinIO class write timing.
+#include <DigitalIO.h>
+
+// Class with runtime pin numbers.
+PinIO pin(13);
+
+void setup() {
+  // Set mode to OUTPUT.
+  pin.mode(OUTPUT);
+}
+void loop() {
+  pin.high();
+  pin.low();
+  pin.write(1);
+  pin.write(0);
+  pin.toggle();
+  pin.toggle();
+  delay(1);
+}