* Implement AddressSet in terms of a generic Set
* Add Uint256Set
* Add EnumerableMap
* Fix wording on EnumerableSet docs and tests
* Refactor ERC721 using EnumerableSet and EnumerableMap
* Fix tests
* Fix linter error
* Gas optimization for EnumerableMap
* Gas optimization for EnumerableSet
* Remove often not-taken if from Enumerable data structures
* Fix failing test
* Gas optimization for EnumerableMap
* Fix linter errors
* Add comment for clarification
* Improve test naming
* Rename EnumerableMap.add to set
* Add overload for EnumerableMap.get with custom error message
* Improve Enumerable docs
* Rename Uint256Set to UintSet
* Add changelog entry