Update entity address scheme in documentation

[Flix6x]

Docstrings of all API endpoints that mention entity addresses should be updated to describe the fm scheme. For example, here is an excerpt from the postMeterData documentation:

"connections": [
    "CS 1",
    "CS 3"
],

I propose to use the fm0 scheme in documentation of API endpoint versions preceding version 2.0. I'm on the fence if we should already be documenting fm1 for version 2.0. Given that the control endpoints (getDeviceMessage, postUdiEvent) are not part of fm1 yet, this would result in mixed documentation.

[Flix6x]

This has gotten some attention in #290, in which at least the documentation for API version 2.0 has been updated, indeed, with mixed documentation.

[Flix6x]

We will leave the documentation for API versions 1.0 to 1.3 as is, since they will be deprecated soon.