Extend the possibility to override AmplitudeLog logic

[alok1111]

Summary

I'd like Amplitude to use my system logger. Current AmplitudeLog and LogMode implementations don't allow me to reuse the logic from com.amplitude.AmplitudeLog#log method.
Sample implementation:

    private class AmplitudeLogWrapper extends AmplitudeLog {
        @Override
        public void log(String tag, String message, LogMode messageMode) {
            if (messageMode.level >= logMode.level) {
                if (messageMode.level >= LogMode.ERROR.level) {
                    log.error(tag + ": " + message);
                } else {
                    log.info(tag + ": " + message);
                }
            }
        }
    }

com.amplitude.AmplitudeLog#logMode and com.amplitude.AmplitudeLog.LogMode#level fields are inaccessible due to AmplitudeLog and LogMode implementations.
Please add corresponding getters as we can only use reflection to get the values.

Motivations

More friendly API that doesn't force you to use reflection.

[yuhao900914]

Thanks for choosing amplitude. We appreciate your feedback.
The new version has the support to access logMode and logLevel. Please check it out.
Thanks.