Updates to support alternative accelerometer and magnetomter sensors

Minor updates to make use of new functionality in microbit-dal that performs
autodetection of attached sensors and instatiation of drivers. Also some code
cleanups to remove unused code.

More specifically:

- Changed MicroBitAccelerometer and MicroBitCompass objects to be references.
  This is to support dynamic autodetection and instantiation of drivers for such hardware.
- Updates to initialise MicroBitAccelerometer and MicroBitCompass references
  through the MicroBitAccelerometer::autoDetect() and MicroBitCompass::autoDetect() methods, respectively.
- Add storage object to MicroBitCompassCalibrator constructor to enable
  persistent storing of calibration data.
- Updated use of accelerometer updateSample() to more commonly used getSample()
  method to improve clarity and to provide a reference example.
- Exposed sensor IRQ lines via MicroBitIO.
- Removed redundant include of Matrix4.h

inc/MicroBit.h

@@ -33,7 +33,6 @@ DEALINGS IN THE SOFTWARE.
 #include "MicroBitDevice.h"
 #include "ErrorNo.h"
 #include "MicroBitSystemTimer.h"
-#include "Matrix4.h"
 #include "MicroBitCompat.h"
 #include "MicroBitComponent.h"
 #include "ManagedType.h"
@@ -112,8 +111,8 @@ class MicroBit
     MicroBitButton              buttonA;
     MicroBitButton              buttonB;
     MicroBitMultiButton         buttonAB;
-    MicroBitAccelerometer       accelerometer;
-    MicroBitCompass             compass;
+    MicroBitAccelerometer       &accelerometer;
+    MicroBitCompass             &compass;
     MicroBitCompassCalibrator   compassCalibrator;
     MicroBitThermometer         thermometer;
 

source/MicroBit.cpp

@@ -68,9 +68,9 @@ MicroBit::MicroBit() :
     buttonA(MICROBIT_PIN_BUTTON_A, MICROBIT_ID_BUTTON_A),
     buttonB(MICROBIT_PIN_BUTTON_B, MICROBIT_ID_BUTTON_B),
     buttonAB(MICROBIT_ID_BUTTON_A,MICROBIT_ID_BUTTON_B, MICROBIT_ID_BUTTON_AB),
-    accelerometer(i2c),
-    compass(i2c, accelerometer, storage),
-    compassCalibrator(compass, accelerometer, display),
+    accelerometer(MicroBitAccelerometer::autoDetect(i2c)),
+    compass(MicroBitCompass::autoDetect(i2c)),
+    compassCalibrator(compass, accelerometer, display, storage),
     thermometer(storage),
     io(MICROBIT_ID_IO_P0,MICROBIT_ID_IO_P1,MICROBIT_ID_IO_P2,
        MICROBIT_ID_IO_P3,MICROBIT_ID_IO_P4,MICROBIT_ID_IO_P5,
@@ -78,7 +78,8 @@ MicroBit::MicroBit() :
        MICROBIT_ID_IO_P9,MICROBIT_ID_IO_P10,MICROBIT_ID_IO_P11,
        MICROBIT_ID_IO_P12,MICROBIT_ID_IO_P13,MICROBIT_ID_IO_P14,
        MICROBIT_ID_IO_P15,MICROBIT_ID_IO_P16,MICROBIT_ID_IO_P19,
-       MICROBIT_ID_IO_P20),
+       MICROBIT_ID_IO_P20, MICROBIT_ID_IO_INT1, MICROBIT_ID_IO_INT2, 
+       MICROBIT_ID_IO_INT3),
     bleManager(storage),
     radio(),
     ble(NULL)
@@ -211,7 +212,7 @@ void MicroBit::onListenerRegisteredEvent(MicroBitEvent evt)
         case MICROBIT_ID_GESTURE:
             // A listener has been registered for the accelerometer.
             // The accelerometer uses lazy instantiation, we just need to read the data once to start it running.
-            accelerometer.updateSample();
+            accelerometer.getSample();
             break;
 
         case MICROBIT_ID_THERMOMETER: