Accelerometer::updateSample should be defined on the base class

[pelikhan]

We call this method to launch the accelerometer - it should be defined on the base class.

        /**
          * Reads the acceleration data from the accelerometer, and stores it in our buffer.
          * This only happens if the accelerometer indicates that it has new data via int1.
          *
          * On first use, this member function will attempt to add this component to the
          * list of fiber components in order to constantly update the values stored
          * by this object.
          *
          * This technique is called lazy instantiation, and it means that we do not
          * obtain the overhead from non-chalantly adding this component to fiber components.
          *
          * @return DEVICE_OK on success, DEVICE_I2C_ERROR if the read request fails.
          */
        int updateSample();