fix: detailed response of parsing EIP4361

[JeneaVranceanu]

Enhanced EIP4361 feature: EIP4361.validate(...) returns validation object that holds:

• isEIP4361 flag that tells if the message given for validation represents EIP4361;
• isValid - tells if EIP4361 message is meeting all requirements;
• optional EIP4361 that is safe to force unwrap if isValid equals true;
• a dictionary of all successfully extracted (not parsed) fields with raw values for each field. Values are accessed by a new enum EIP4361Field.

This combination allows getting the reason for failed message parsing, e.g. if capturedFields does not contain value for EIP4361Field.address it's safe to assume that message does not contain the address field which is required.