Next steps on readout documentation

[jcfreeman2]

There's lots of good material already, but here are a couple of things that could be done:

In the README.md, I like the "get things running right away" approach. Some material is out of date, however: e.g., in the fakereadout-commands.json users are instructed to run with, the plugin BufferedFileStreamer is used though it got renamed DataRecorder about a month ago. Also, is there anyone who might want to run fakereadout-commands.json who wouldn't also be modifying the code? If so, then perhaps we should move fakereadout-commands.json out of test so it gets installed as part of the readout package.

I think what's already in the "Functional Elements" section is great. I'm wondering if it would be useful to add links to the relevant headers for each of the listed Domains, with a very brief description. E.g., for the "Trigger Primitive (TP) handling domain" section, add a line roughly like RawWIBTp.hpp: Trigger Primitive model, TpHeader + TpData + TpPedinfo

Also, it would be nice to add a very brief description of the other components of the package (in particular, the DAQ modules), which users could all see in the same location:
FakeCardReader: non-hardward generation of user payloads at a given rate, from WIB to FELIX binary capture
DataRecorder: : write WIB superchunks to file
...etc...