txns of type NORMAL should not call contracts

[kroggen]

These changes are intended to be implemented on hardfork V4:

• Transactions with type NORMAL should not call smart contracts
• Transactions with type TRANSFER can only interface with smart contracts on these conditions:
  • The amount must be greater than 0
  • The payload must be empty

To transfer native Aergo tokens to a smart contract for a function that is not named "default" or that requires arguments, we must use a transaction with type CALL