Add ERC for wallet_getOwnedAssets (#2256)
* Add ERC for wallet_getOwnedTokens JSON-RPC method
* Add EIP number & discussions URL to EIP-2256
* Fix wallet_getOwnedTokens input arguments
* Add chainId as argument to wallet_getOwnedTokens
As suggested in https://github.com/ethereum/EIPs/pull/2256#issuecomment-526204181
* Rename EIP-2256 method to wallet_getOwnedAssets, align data struct with EIP-747
Based on the discussions up to and including this comment: https://ethereum-magicians.org/t/eip-2256-add-wallet-getownedassets-json-rpc-method/3600/15
- rename `wallet_getOwnedTokens` to `wallet_getOwnedAssets`
- use `options` in the response field, as EIP-747 proposes, to allow for different asset-specific information to be returned
- use `asset` instead of `token` where generalization is needed
- replace `interface` with `type`, to align with EIP-747
- add `types` as a filter field
- add `decimals` as an optional field in `options`
* Fix category for EIP-2256 - use Interface
As suggested in https://github.com/ethereum/EIPs/pull/2256#discussion_r321153237
* Add justification field for EIP-2256, s/count/limit
- add `justification` field in the request arguments, as suggested in https://github.com/ethereum/EIPs/pull/2256#issuecomment-527683267
- replace `count` with `limit`, as `count` is more ambiguous (as revealed in https://github.com/ethereum/EIPs/pull/2253#discussion_r320140105)
GitHub Diff