Adds support for per-column statistics targets and reloptions to the Rails schema.rb file.

(The name "innumerate" was chosen when the library only supported statistics targets. It was a weak joke at the time, and now the name makes so sense at all. C'est la vie.)

In your ActiveRecord migrations, you can use:

set_statistics_target :users, :email, 1000

... to set the statistics target of users.email to 1000. To make the migration reversible, use the old_target option:

set_statistics_target :users, :email, 1000, old_target: -1

Note that -1 means "use the server's default statistics target."

You can also set a table's reloptions with:

set_reloptions :users, {
  fillfactor: 70,
  autovacuum_vacuum_insert_threshold: 40000
}

There is also a version that only sets a single reloption:

set_reloption :users, :fillfactor, 70

(This is the version used in the schema.rb file, since it will remain tidy, even if you add many reloptions to a single table.)

Reloption changes are not currently invertable.