Refactro UniversalNFTCore to support ERC1155

[andresaiello]

The file

https://github.com/zeta-chain/standard-contracts/blob/main/contracts/nft/contracts/zetachain/UniversalNFTCore.sol

includes the logic for zetachain transfer but also some ERC721 specific. Split it in two file (UniversalNFTCore.sol and UniversalNFTCore721.sol) and the we can reuse the same logic for a 1155 version. Should add some more small changes but are out of the scope of this issue.