Mihai Schiopu

- Pending the PubkeyConverter refactoring and sovereign chains, the actual hrp `erd` should not be a constant and unchangeable value. - Changes: 1. `Address(..)` accepts now an optional hrp, other...

#### Description of the pull request (what is new / what has changed) Made some fixes that came from community see [issue](https://github.com/ElrondNetwork/docs.elrond.com/issues/469). Documented breaking changes in `/sdk-and-tools/erdjs/erdjs-migration-guides/` for erdjs v12...