Implementation of a new VM for the contract runtime that will execute WebAssembly

[mpapierski]

@RitaMAllenCA @rafal-ch

Yesterday's meeting notes:

• Good progress so far, we have basic input passing, calling exports
• On contract SDK there are macro-based exports hiding all the unnecessary boilerplate, and basic compile-time schema generator.
• There's an established convention for passing inputs (previously: named arguments "late bind" that allows you to ask for specific arg, now early bind "chunk of bytes" that you have to parse)
• Abstract key-value storage makes it possible to hook up the casper-storage trie.

Further steps:

• Contract Versioning is a core feature, we should keep it in the new VM
• Keep in mind backwards compatibility RuntimeArgs (we think it will work out of the box by passing serialized RuntimeArgs)
• Next, focus on creating smart contracts, and calling into smart contracts.
• Keep in mind backward compatibility and upgrade story for 1.x contracts with regards to named keys etc.