Support v6 API

[Joe Shaw]

It looks like the v5 API we were previously using has been discontinued and no longer works.

There is a new v6 API that is mostly the same, but requires OAuth for authentication. Some new info on that here:

https://github.com/hjdhjd/homebridge-myq/blob/master/src/myq-api.ts#L21
arraylabs/pymyq#67

Looks like it's going to be a fairly involved update.