Adding support for ERC 1271

[Muhammad-Altabba]

This pull is to add support for ERC 1271 and it includes:

• Upgrading truffle to version 5.1.43 which includes:
  • Upgrading solidity code to v0.5.16 and handle its breaking changes
  • Updating test cases code for the breaking changes of Web3 v1.2.1
• Adding checkSignature' and other methods overloading to EthereumDIDRegistryto make it compatible withERC1271`
• Adding test cases Signed methods …
• Writing tests for using Contract Signature at EthereumDIDRegistry
  • Also, test the Smart Contract overlading methods that accept the composed signature that is signed by a private key
  • And, add a simple ERC1271 Sample contract and use it in the test cases.

[ottomorac]

hello @mirceanis , as @andresobandoalfaro pointed out this code worked really well for us. You way want to consider merging it in. Thank you!!