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/PinIOBegin/PinIOBegin.ino

@@ -0,0 +1,24 @@
+// Use begin to assign pin numbers.
+// Read pin 12 and write the value to pin 13.
+#include <DigitalIO.h>
+
+// Declare the PinIO instances.
+PinIO readPin;
+PinIO writePin;
+//------------------------------------------------------------------------------
+void setup() {
+  // Assign pin 12 to readPin.
+  readPin.begin(12);
+  
+  // input mode with pull-ups disabled
+  readPin.config(INPUT, LOW);
+
+  // Assign pin 13 to writePin and set mode to output.
+  writePin.begin(13);
+  writePin.mode(OUTPUT);
+}
+//------------------------------------------------------------------------------
+void loop() {
+  // Copy the value read from readPin to writePin.
+  writePin.write(readPin.read());
+}