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

[kroggen]

Tests to be added:

On hardfork_version >= 4

Should work:

• Transfer Aergo to contract using TRANSFER type

Should fail:

• Transfer Aergo to contract using TRANSFER type, contract without function "default"
• Transfer Aergo to contract using TRANSFER type, contract function "default" not payable
• Transfer Aergo to contract using TRANSFER type, payload not empty (hash)
• Transfer Aergo to contract using TRANSFER type, payload not empty (JSON for call)
• Transfer Aergo to contract using TRANSFER type, amount = 0

Then repeat the above using NORMAL type

On hardfork_version < 4

Should fail:

• Transfer Aergo to contract using TRANSFER type, contract without function "default"
• Transfer Aergo to contract using TRANSFER type, contract function "default" not payable
• Transfer Aergo to contract using TRANSFER type, payload not empty (hash)

The same for NORMAL type

Should work:

• Transfer Aergo to contract using TRANSFER type
• Transfer Aergo to contract using TRANSFER type, payload not empty (JSON for call)
• Transfer Aergo to contract using TRANSFER type, amount = 0

The same for NORMAL type

[hayarobi]

@ultrafellen Do you agree with this policy?

[ultrafellen]

I'm not sure about the code, but I agree with the policy.

[hayarobi]

lgtm