Add recruitment workflow

[jace]

Hasjob currently only makes connections between employers and candidates, and assumes further interactions will be over email.

This makes the follow-up process cumbersome for employers not using an ATS, and offers no visibility to candidates on their status.

Hasjob should implement a rudimentary ATS with an employer-customisable workflow similar to this: https://trello.com/b/vxaknkci/hiring-process

Tentative: candidates should be able to see each employer's workflow and where they are in it.

[ghost]

ATS?

[jace]

Applicant Tracking System, what services like RecruiterBox and this badly named company provide.

[jace]

Related: #352