Implement ERC-3525

[moconnell]

EIP-3525 describes a semi-fungible token (derived from EIP-721 Non-Fungible Token Standard), where tokens with the same "slot" value are fungible with one another.

We intend to utilise this feature in order to facilitate the splitting and merging of tokens related to a single impact claim certificate.

Reference Implementation

EIP-3525 implementation

Pre-requisite for:

• https://github.com/protocol/hypercerts-docs/issues/16
• https://github.com/protocol/hypercerts-docs/issues/17
• https://github.com/protocol/hypercerts-docs/issues/19

Technical

• [x] Add 3525 contract based on reference implementation
• [x] Add 3525 test suite
• [x] Update Hypercert contract to inheret 3525 and update logic to use 3525
• [x] tokenURI and slotURI are -for now- identical and return a metadata JSON built with on-chain data
• [x] add name, description and fractions[] to calldata and parse accordingly
• [x] msg.sender is owner for all fractions