Write firmware version in config block

[sneakers-the-rat]

Related to: #64

One thing that makes it tricky to support different scopes in mio is that when there are changes in the other projects, there isn't a programmatic way for us to know it in mio, so we end up needing to make the implementations there much more complex than they need to in order to accommodate all the sources of potential variability.

A very simple way around this is to simply give each version of the firmware a version and then write that in the config block. It can be a single integer if you don't want to go to the trouble of doing semver or whatever in 3 values, but e.g. if we had a version number then we could just declaratively configure wirefree scopes: ok you have version x, that means you use this config.