Create self-sovereign identity contracts via API

[kern]

As a Cleargraph user
I want to create ERC 725 identity contracts
So that I can use a persistent, self-sovereign identity in decentralized applications

[kern]

Implemented mutations to check for username availability and phone number verification. Right now there's a stub for the createIdentityContract mutation. Next up is to implement the factory contract interface and get this thing working on testnets!