Set uBit.io.logo to capacitive touch mode by default. (#418)

Without initialising the touch engine in the background.

model/MicroBit.cpp

@@ -116,17 +116,14 @@ MicroBit::MicroBit() :
     }
     */
 
-    // Configure serial port for debugging
-
-    //SERIAL_TODO:
-    // serial.set_flow_control(mbed::Serial::Disabled);
-    //serial.baud(115200);
-
     // Enable the serial port as a deep sleep wake event. (Useful for MicroPython REPL, for example)
     #if CONFIG_ENABLED(MICROBIT_USB_SERIAL_WAKE)
         serial.status |= CODAL_SERIAL_STATUS_DEEPSLEEP;
     #endif
 
+    // uBit.logo is a Capacitive TouchButton, ensure the io pin is set capacitive as well
+    io.logo.status |= IO_STATUS_CAPACITATIVE_TOUCH;
+
     // Add pullup resisitor to IRQ line (it's floating ACTIVE LO)
     io.irq1.getDigitalValue();
     io.irq1.setPull(PullMode::Up);