Two Factor Authentication

[egeldenhuys]

We will be using speakeasyjs for 2FA.

It will be most flexible if we make 2FA optional.

Process:

1. Client sends Credentials as normal
2. Server responds in a way that indicates 2FA is required
3. Client sends code from 2FA code generator
4. Server validates and returns Auth token as normal

Depends on: TripleParity/docks-api/issues/67

[egeldenhuys]

Closed by #166