Remove walkin test model
First pass at walk-in stuff

Add columns and templates to Walk-in model; move from triage to doctor
lists etc.

Refs openhealthcare/elcid#292, openhealthcare/elcid#298,
openhealthcare/elcid#398, openhealthcare/elcid#291,
openhealthcare/elcid#293, openhealthcare/elcid#295