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/DigitalPinReadWrite/DigitalPinReadWrite.ino

@@ -0,0 +1,11 @@
+// Read pin 12 and write value to pin 13.
+#include <DigitalIO.h>
+
+DigitalPin<12> pin12(INPUT);
+DigitalPin<13> pin13(OUTPUT);
+
+void setup() {}
+
+void loop() {
+  pin13 = pin12;
+}