Utilize ERROR_* codes as return value defined in globals.h

[harrisonCassar]

As I was working to implement #55, I realized that the update method of the LSM6DS33 could better describe the reason for failing through utilizing some of the error codes we already have defined in src/globals.h. Perhaps we might need to add a few more to better express what went wrong for this specific function.

SPARTAN/Software/src/sensors/lsm6ds33.cpp

Lines 166 to 201 in d8d46cb

	// TODO(harrisoncassar): Update this `update` function to utilize `ERROR_*` enums defined in `globals.h`
	bool spartan::LSM6DS33::update() {
	if (m_status == STATUS_OFF)
	return false; // Should be returning ERROR_INVALID_STATUS
	if (hasNewData() == RESULT_FALSE)
	//std::cerr << "No new data" << std::endl;
	return false;
	// set I2C address
	if (m_i2c.address(lsm6Address) != mraa::SUCCESS) {
	std::cerr << "Unable to set I2C address." << std::endl;
	return false;
	}
	// read temp,x,y,z (14 bytes) into buffer
	if (m_i2c.readBytesReg(lsm6ds33::OUT_TEMP_L, m_buffer, lsm6ds33::BUFFER_SIZE) == -1) {
	std::cerr << "Unable to read data bytes starting from LSM6DS33_OUT_TEMP_L." << std::endl;
	return false;
	}
	//record rawacceleration values using data reads for x,y,z respectively
	//DATAx0 is the least significant byte, and DATAx1 is the most significant byte
	//conversion of raw sensor data into relevant values based on constant offset values
	m_temp = ((m_buffer[1] << 8) | m_buffer[0]);
	m_gyro.x = ((m_buffer[3] << 8) | m_buffer[2]);
	m_gyro.y = ((m_buffer[5] << 8) | m_buffer[4]);
	m_gyro.z = ((m_buffer[7] << 8) | m_buffer[6]);
	m_accel.x = ((m_buffer[9] << 8) | m_buffer[8]);
	m_accel.y = ((m_buffer[11] << 8) | m_buffer[10]);
	m_accel.z = ((m_buffer[13] << 8) | m_buffer[12]);
	return true;
	}

Make sure when you change the return value of this function, its invocations also respect the new return value (and handle all of the possible return values properly).

Related to #56.