(cherry picked from commit 225b4921)

(cherry picked from commit d8cbd555)

* move BreakInvariantBounty to drafts

* fix bad imports

* rename Index.currentId to current

* use += operator for clarity

* rename Counter.Index to Counter.Counter

* move Counter to drafts

(cherry picked from commit 3e55408c)

(cherry picked from commit b4f87bb8)

(cherry picked from commit c12a1c68)

* add logo

* new readme

* add large logo

* improve readme

* Update README.md

* add link to guides

* remove leftover sentence

* Extract standard token behaviuor to reuse it in other tests

* Add opt in ERC20 migration contract

* Make migration contract not to depend from standard token

* Changes based on feedback

* Improve MigratableERC20 inline documentation

* move behaviors to behaviors directory

* refactor MigratableERC20 into ERC20Migrator

* fix errors

* change expectEvent to support multiple events with same name

* fix tests

* update documentation

* rename MigratableERC20 files to ERC20Migrator

* move to drafts

* test beginMigration

* rename to ERC20Migrator

* missing semicolon  (╯°□°）╯︵ ┻━┻

* add non-zero check

* improve documentation based on review comments

* improve test descriptions

* improve docs

* add getters

* fix contract

* improve tests

* Split enumerable and metadata implementations.

* Renamed ERC721Basic to ERC721, and ERC721 to ERC721Full.

* Fixed linter errors.

* The role library now requires non-zero addresses.

* Fixed SignatureBouncer checks with null address.

* change ternary operator for or operator

* adapt to new variable name convention

* Update Roles.sol

* Remove the Minted event

* Remove the TokensBurned event

* Remove unused