Improve GPS EXIF parameters comments.

    // should not set default value for this parameter.

    // Example value: "0" or "90" or "180" or "270". Write only.

    static const char KEY_ROTATION[];

    // GPS latitude coordinate. This will be stored in JPEG EXIF header.

    // Example value: "25.032146". Write only.

    // GPS latitude coordinate. GPSLatitude and GPSLatitudeRef will be stored in

    // JPEG EXIF header.

    // Example value: "25.032146" or "-33.462809". Write only.

    static const char KEY_GPS_LATITUDE[];

    // GPS longitude coordinate. This will be stored in JPEG EXIF header.

    // Example value: "121.564448". Write only.

    // GPS longitude coordinate. GPSLongitude and GPSLongitudeRef will be stored

    // in JPEG EXIF header.

    // Example value: "121.564448" or "-70.660286". Write only.

    static const char KEY_GPS_LONGITUDE[];

    // GPS altitude. This will be stored in JPEG EXIF header.

    // Example value: "21.0". Write only.

    // GPS altitude. GPSAltitude and GPSAltitudeRef will be stored in JPEG EXIF

    // header.

    // Example value: "21.0" or "-5". Write only.

    static const char KEY_GPS_ALTITUDE[];

    // GPS timestamp (UTC in seconds since January 1, 1970). This should be

    // stored in JPEG EXIF header.