Multiple Database Support - #10

Can we scope down the changes - currently a lot of styling and files are changed across. However, focussing on just the important changes

1. I have a similar comment in PR SQL Decorator created for TABLE_SCHEMA creation #11 but it might be a good idea to move the prompts to a jinja2 template. That way, the dialect is just an additional variable available and jinja if blocks can be used to get the correct prompts.
2. Extract schema from DB - This by itself can be a separate PR. So two different smaller PRs are easier to get merged.
3. Too many new dependencies are added. Think about removing some of them and adding some of them as packages e.g. foundation-sql[postgres], foundation-sql[mysql] etc. The user (developer) should be incharge of which optional dependencies they want to include. Some of that would also need to be modified in setup.py
4. It would be interesting to think of the tests as multi-db tests i.e. we should be able to run the same BasicTest across mysql, sqlite, postgres and so on.

Overall, looks good. Would just want to break it into smaller change, avoid style only changes and improve on some of the above. Looking forward to getting this merged ... 👍

• Another pr for Schema Extraction from the DB has been raised before this one.
  Schema lookup implementation #9
• Since this pr is dependent on that one, once it is merged, this PR’s diff will only show the new changes related to dialect support.
• Will update to use jinja blocks to get the prompts instead and make dependecies optional