Update smart contract from Solidity 0.4 to Solidity 0.5 + ABIEncoderV2 tutorial

In this tutorial we will learn how to update a smart contract from Solidity 0.4 to Solidity 0.5.

Solidity 0.5 was released last year in 2018 but a lot of the existing smart contracts and tutorials are still written for Solidity 0.4. It's important to be able to understand the difference between both versions and to update your old code the new version of Solidity.