GeoAlchemy support for GIS database column types

[leogaggl]

Things to check first

• I have searched the existing issues and didn't find my feature already requested there

Feature description

Firstly thank you for making this available - great work!

It would be great to see if this can work with GeoAlchemy2 which apparently works with (older versions of) sqlacodegen (https://stackoverflow.com/questions/34594165/sqlacodegen-issue-with-geometry-type).

I am unsure where to import the GeoAlchemy Geometry?

Use case

We ingest some data that we want to store in GIS types to allow for geo functions in Postgres.

It would be excellent to have this flow through to SQLAlchemy and GeoAlchemy

[leogaggl]

Just as further info. Currently I get this warning:

cli.py:59: SAWarning: Did not recognize type 'geography' of column 'geo_location'
  metadata.reflect(engine, schema, not args.noviews, tables)