Wip/bolus wizard bg mmol units

[sulkaharo]

Now running this in production and it works. I changed this to report the values in mgdl, as it's way easier to handle the data if decocare just decodes to one set of units consistently. So LGTM with my patch.

[bewest]

Not sure how I feel about this. Decocare is supposed to be stupid simple, like curl, it was originally a tool to tell exactly what is going on inside the device. In the past, I've been pretty disciplined/strict about separating conversions: https://github.com/openaps/openaps/blob/master/openaps/vendors/units.py, I think we're at a point where a better openaps medtronic should be created to make a lot of this easier: an oref0 version of the medtronic vendor.