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/testFastDigital/testFastDigital.ino

@@ -0,0 +1,13 @@
+// Test fastDigital function timing with a scope.
+#include <DigitalIO.h>
+const uint8_t PIN = 13;
+void setup() {
+  fastPinMode(PIN, OUTPUT);
+}
+void loop() {
+  fastDigitalWrite(PIN, HIGH);
+  fastDigitalWrite(PIN, LOW);
+  fastDigitalToggle(PIN);
+  fastDigitalToggle(PIN);
+  delay(1);
+}