Add battery status for G930

[tobiaspc]

I simply ported (copied actually) it from https://github.com/Roliga/g930-battery-percentage

Seems to work quite good.

Issues:

• Charging status is not read from the device
• Runtime / Charge time is not read
• During Charge, battery goes over 100%

I believe the code directly reads the voltage, maybe someone can improve that in a later step.

This is my first pullrequest, is everything in order?

[Sapd]

Thanks for your submission, I made some comments.

I think the battery goes over 100%, because the battery of the owner of the other repository was already quite old and wasn't able to charge it completely.
You can probably set BATTERY_MAX safely to 100.

[tobiaspc]

Thanks for the quick review, I think everything should now be correct.
My device is also quite old (from ~2012).
After a full day of charging, the program reports 100% with the current upper limit of 91. So either that limit is correct, or my battery is also dying.
Since I am about to replace the battery in a few days, I can verify the upper limit then with a fresh one.

If you want, you can pull this branch now. Either way, i am willing to investigate the protocol further, in order to get charging state / remaining time.

[Sapd]

Yes, I included the current state.