Column values sort

[clrcrl]

Opening in place of #289 — needed to rebase to get it to work, and while I was here I simplified the implementation a little

This is a:

• new functionality — please ensure the base branch is the latest dev/ branch
• a breaking change — please ensure the base branch is the latest dev/ branch — changes positional argumenet order

Description & motivation

Implement an order_by arg to get_column_values. Fix up docs while here

Checklist

• I have verified that these changes work locally on the following warehouses (Note: it's okay if you do not have access to all warehouses, this helps us understand what has been covered)
  • BigQuery
  • Postgres
  • Redshift
  • Snowflake
• I have updated the README.md (if applicable)
• I have added tests & descriptions to my models (and macros if applicable)
• I have added an entry to CHANGELOG.md

[clrcrl]

@jtcohen6 — can I get your eyes on this. Namely, I'm curious whether order_by feels like the right argument name (sort?). We also at some point should deprecate the table argument name but that feels like more than I want to do right now to get this backlog down

[jtcohen6]

Namely, I'm curious whether order_by feels like the right argument name (sort?).

Thinking only about the nomenclature, I'd feel equally fine about order_by and sort_by. I like order_by because it neatly maps to what's happening being run behind the scenes: it's actually order by in the query, rather than (say) a sort Jinja filter on the returned query results.