2.1.0-beta3 - Verifier & Gateway

Added

• Implemented a new contract Gateway to interact with the IdFactory. The Gateway contract allows individual
  accounts (being EOA or contracts) to deploy identities for their own address as a salt. To deploy using
  a custom salt, a signature from an approved signer is required.
• Implemented a new base contract Verifier to be extended by contract requiring identity verification based on claims
  and trusted issuers.