Databricks catalog not in schema

[matthewchoy-envisso]

Databricks model config "catalog" is not in the schema.

I have a use case to set the catalog based on environment variables, in order to deploy many copies of the same DBT project for different clients.

Seems like it should be simple to add "catalog" and "+catalog" to the schema, similar to #75.

[joellabes]

Sounds good! I'd welcome a PR to add this 🎉

[matthewchoy-envisso]

@joellabes Raised the PR, let me know if anything else is needed.