Refs #52 — Have 6 digits lengths for short verification code.
Merge pull request #52 from mozilla-services/52-shortVerificationCode

Define how should look like the MT manual code.
Refs #58 - Refs #59 — Link everything to hawkId.
Refs #59 — Upgrade the MOMT workflow.
Fix #56 — Be able to ask for long or short verificationCode. on /sms/mt/verify
Alexis review.