* Align ERC721 Receiver with current ERC721 standard. Adds a second address field to onERC721Received onERC721Received(address,address,uint256,bytes) Updates the function signature to 0x150b7a02 from 0xf0b9e5ba * Add _operator to onERC721Received * Fix error caused by formatOnSave * Fixed comments on ERC721Receiver Removed "Must use 50,000 gas or less" Corrected the function signature