Add a fungible asset standard
Problem: FA1.2 inherits some problems from ERC-20, namely:
- No way for token holder to reject a transfer (apart from the basic allowance mechanism which may not be useful for all use cases).
- No way for a token receiver to reject a transfer.
- No way to notify the receiver that the transfer has occurred via on-chain mechanisms.
Solution: Propose FA1.3 that aims to solve these problems.