Allow to exclude all rules that break clients

[kudrevatykh]

There are a lot of rules that helps not to break existing clients. For example ban-drop-not-null and ban-drop-table It whould be nice if user can exclude all such rules with one option and leave only rules that cause exlusive locks and data rewrite.

[chdsbd]

We could add another value to the —exclude option, like: backwards-compatibility, locking, schema-style

For the documentation website we already define groups like this with tags: https://github.com/sbdchd/squawk/blob/99e93139f430deebc703d0123d398d25fa946550/docs/src/pages/index.js#L105

We could also add a new flag to be more explicit, like —-exclude-group