Prototype Smart Contract reworking

[gregLibert]

No description provided.

[gregLibert]

The idea is to be able to create a basic smart contract doing something like:

import { u256 } from "as-bignum/assembly";
import { ERC20Impl } from "@massalabs/sc-standards/smart-contract/erc20/assembly";
export * from "@massalabs/sc-standards/smart-contract/erc20/assembly/exportable/erc20Core";

// @ts-ignore
@global const FungibleToken = new ERC20("USD", "$", 9, u256.fromU32(1000));

Or, for a mintable version:

import { u256 } from "as-bignum/assembly";
import { ERC20Impl, Exportable } from "@massalabs/sc-standards/smart-contract/erc20/assembly";
export * from "@massalabs/sc-standards/smart-contract/erc20/assembly/exportable/erc20Mintable";

// @ts-ignore
@global const FungibleToken = new ERC20("USD", "$", 9, u256.Zero);

const minter = new Address("AU1...");

export function mint(args: StaticArray<u8>): void{
  assert( Context.caller() == minter, "Forbidden");
  Exportable.mint(args);
}