Add support for Materialized Views

[jayadevanm]

The documentation does mention that Views are not supported. It looks like Materialized Views are also not supported, though they are more like tables than views. We can create indexes, they contain data etc.

[bplunkett-stripe]

It's unfortunately not the straight forward (think webs of dependencies), but I do intend to add support for them and have a mental model in my head as to how I will achieve it. I first would like to refactor the SQL generation a bit before I implement (materialized) views.