feat: [v2] Config conversion and validation code from one data file

[kentquirk]

This is the beginnings of a multi-pronged approach to data conversion.

We want a tool that can read an existing V1 config file and generate a new one, omitting no-longer-needed values and reformatting others, and generating a properly commented YAML file that is up to date with Refinery's capabilities.

We also want a validation library that can check a config completely. The best way to do that is with a JSON Schema validator, which in turn needs a JSON Schema data file that expresses the constraints on the fields.

Since both of these things need a lot of information about all the fields in the config, this PR creates one big data file that will contain enough information to solve both problems, and I'm planning to generate both the template for the converter and the JSON schema from the same data file.

In scope for this PR:

• create config converter that uses a template to convert
• create data file containing details of config items
• create tool for generating the template from the data file
• create rough structure of new config
• manually check every field
• settle on the final design of config structure
• adjust config structure to that design
• finish config converter tool
• document config converter tool

NOT in scope:

• adapt Refinery's config structure to this new design
• do anything with validation schema (this includes additional annotations to support schema -- these will come later)

[kentquirk]

The config format and this tool are now in good enough shape to move on to other things; we will revisit before final release.

[kentquirk]

There is now a single executable with subcommands(rather than running things as tests) with a Makefile to drive the non-converter commands. I've also done a go:embed so that the executable stands alone without need for external template or data files. And I've put summaries back and edited the descriptions so they're not redundant to the summaries.

[kentquirk]

I just added docs generation for config; it writes out config.md.