Provide docs and tools for an opinionated development workflow

[binste]

Could look something like:

1. dbt-ibis develop -s stg_customers -> Converts stg_customers.ibis to stg_customers.ibis, unpacking the model function for easier editing and keeping the rest of the code the same
2. Easy way to turn refs and sources into Ibis tables. Initially, it's probably "bring your own Ibis connection". In a second step, could try to create it based on dbt profiles, at least for simple cases?
3. Users can then in the notebook interactively run the code and modify the model
4. Some command to turn it back into an .ibis file.

This PR just contains some first attempts. More to come... Constructive feedback is very welcome!