The format of this config value was changed in v0.35.
- Move plan to its own file (for ease of reading).
- Convert indexer string to an array if not already done.
Right now the confix tool works up to v0.35. This change is preparation for
extending the tool to handle additional changes in v0.36.
Mostly this is adding documentation. The one functional change is to fix the
name of the moved "fast-sync" parameter, which was renamed "enable".
- Document the origin of each transformation step.
- Update fast-sync target name.
