FT NEP-141 require having minting/burning interface

[telezhnaya]

We finished the work on support of NFT #254 #256 🎉
It's better to read NFT events standard at first, since we want to do the pretty same thing for FTs.
Current FT doc: https://nomicon.io/Standards/FungibleToken/README.html

Some initial thoughts:

• The work here should go much easier, we can take the same approach as in FTs: we use logs to imitate the events.
• For one smart contract, we have at most one FT associated with it. Is it true? If so, we don't need to pass token_id. UPD: no, it's not true for MultiToken standard. So we have to pass token_id even in a simple FT contract.
• We have the new field: amount, it should be provided in the highest precision for each smart contract.
• We need to re-check that we don't have any fees in FT. If Alice transfers 1 FT to Bob, it means that Alice spent exactly 1 FT (and the fee in NEAR, we don't need to think about it, it's not on the smart contract abstraction layer), Bob received exactly 1 FT.
• We still have 3 types of actions: mint, burn and transfer.
• We still have optional memo field.
• We don't need to add msg field, it's technical field for supporting cross-contract calls, we don't care about that.
• We don't have the support of approval management for FT (approvals in NFT), we even don't have the issue about that, but I've heard we want such functionality. Should we think about approvals at first?
• Do we need batch events? Should we use batch syntax (read: arrays in all places where possible) just because we can?

@mikedotexe I know it's not your war anymore, but if you are ready to participate in any role, you are more than welcome ❤️

@jberrytech @frol @MaximusHaximus
Please tag anyone else who could be interested. Especially I want FT contract developers to be involved

[frol]

cc all subscribers to this issue, please review #300