Medtronic support

[ricklambrechts]

Lots of things to refactor and improve more.

I have added optional with gnu++17 but maybe we do not want this.
Now I have an initial working implementation we can clean it up. As I also do not know all the best practices.

TODO:

• Trend (UP/ DOWN)
• Better error messages
• Discuss caching logic
• Remove optional?

Related to #53.

[ktomy]

Hi,
Looks like a lot of work has been done, thanks a lot!
I can see that for the authentication the end-user has to insert json generated by the https://github.com/ondrej1024/carelink-python-client tool. My fear is that non-technical users will not be able to do it. Even I didn't quite understand from their readme how to get this JSON, where is the input data, where is the output.
Could you please elaborate on this? I was thinking that maybe that python library can be hosted somewhere (I can host stuff on a community server) and we can create an additional UI so that people can retrieve their tokens without having to cloneand execute stuff. After all NSClock is about simplicity :)
Thanks