Don't check the caller in NEP17

[shargon]

This is not needed, and redundat because it's done during the syscall https://github.com/neo-project/neo/blob/736c346b9d8b1404f10023eeecb3a8e92ae0c542/src/neo/SmartContract/ApplicationEngine.Runtime.cs#L216

[roman-khimov]

Yep, #126 (comment)

[shargon]

Yep, #126 (comment)

Maybe we can add just a note, this syscall will compare against the callingScriptHash first..?

[erikzhang]

We need to explain what the contract is supposed to do and give the best practices for doing it in one step using CheckWitness.

[shargon]

We need to explain what the contract is supposed to do and give the best practices for doing it in one step using CheckWitness.

We can add a note like this Take into account that <code>Neo.Runtime.CheckWitness</code> already will check whether the <code>from</code> address equals the caller contract hash.