config init now leaves out the test sources unless given --all

A section tagged init:"hidden" isn't written to the file config init
generates; fts_mock and sleeper are. config init --all writes them too.
They still load, and the config commands read and set them as before.

README.md

@@ -105,7 +105,7 @@ Global flags: `--config`/`-c` (config file), `--debug`/`-d` and
 
 | Command | Purpose |
 |---|---|
-| `job-search config init [path]` | Create a config file |
+| `job-search config init [path]` | Create a config file holding the defaults (`--all` also writes the test sources, `fts_mock` and `sleeper`) |
 | `job-search config show` | Print the configuration (`--json` or `--yaml` for those formats) |
 | `job-search config get <key>` | Print one value, e.g. `logging.level` |
 | `job-search config set <key> <value>` | Validate and write one value to the config file |