Sets Concept Exercise

[BethanyG]

Closes #2296

New concept exercise cater-waiter (sets concept)
Please Note:

1. This exercise has two "data" files that should display in the editor as read-only. I think I've referenced these correctly, but it would be good to double-check them.
2. I've used tooltip-type link references in the hints.md file, but am not sure that they will resolve correctly.

---

• config.json & UUID for exercise
• introduction.md
• instructions.md
• hints.md
• .meta/exemplar.py
• Added exercise icon to .meta/config.json file
• Formatted .meta/config.json file
• sets_test.py (tests)
• sets.py (stub file)
• Added sets_test_data.py & sets_categories.py for exercise constants and test data.
• Added sets_test_data.py & sets_categories.py to .meta/config.json "editor" key
• Formatted config.json file

[BethanyG]

Please someone approve this so it can be merged and put out of my misery. 😆

[iHiD]

Nice work! :)