bancheck: Provide configurations

[empijei]

We should provide some pre-baked configurations:

1. Basic, simple one: this is more of an example than a ready to use thing. The idea would be to showcase how a real configuration would look like.
2. Usable, liberal one: this one is ready to use, and only cares about GSW-related stuff (e.g. preventing import for plugins exceptions, config constructions etc.)
3. Usable, opinionated one: this will block all things from 2, but also stdlib stuff like md5, sql, math/rand etc.