(Refactor) Apply updates of ERC780

[phahulin]

• What is it? (leave one option)
  • (Refactor) proposal (i.e. no new features or updates, just code optimization/library updates)

https://github.com/ethereum/EIPs/issues/780

Unfortunately, erc780 was updated recently and possibility to delete claim about self was removed, now only the issuer can remove a claim it made previously

    function removeClaim(address issuer, address subject, bytes32 key) public {
        require(msg.sender == issuer);

We should

• [x] update erc780 code https://github.com/poanetwork/poa-popa/blob/master/blockchain/contracts/EthereumClaimsRegistry.sol
• [x] update tests https://github.com/poanetwork/poa-popa/blob/master/blockchain/test/ethereum_claims_registry_specs.js#L43
• [x] now we can decrement totalUsers, totalAddresses and totalConfirmed when address is unregistered since we can be sure that no one else can unregister it
• [x] redeploy new version on sokol
• [x] redeploy new version on core