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/testArduino/testArduino.ino

@@ -0,0 +1,14 @@
+// Scope test for write timing with Arduino digitaWrite().
+const uint8_t PIN13 = 13;
+
+void setup() {
+  // Set mode to OUTPUT.
+  pinMode(PIN13, OUTPUT);
+}
+void loop() {
+  digitalWrite(PIN13, HIGH);
+  digitalWrite(PIN13, LOW);
+  digitalWrite(PIN13, HIGH);
+  digitalWrite(PIN13, LOW);
+  delay(1);
+}