Delegate batch signatures for DIP-145

[wilwade]

Problem

Implementation layer should have the details about validation instead of signatures on announcements

See DIP-#145 for details

Closes: #145

Solution

Reduce the validation cost and increase transparency by removing the signature from the individual Announcements and requiring that the implementation have a way to validate. EVM Implementation being that the batch submission is from a user or delegate directly

Change summary:

• [x] Updated Spec Versions
• [x] Remove signatures from Announcements
• [x] Remove Signatures.md file
• [x] Remove createdAt from Announcements as it was only there for replay protection
• [x] Remove other references to signatures for duplicate handling that was required for replay attacks.

Steps to Verify:

1. No more signatures on any Announcement Types
2. No more createdAt on any Announcement Types
3. Version bump for Ethereum implementation