reportDate -> visitDate

Our report date is really a visit date, so this commit makes it
official. Report date is collected as part of the paper trail (it's the
first recorded event).
Resolve moment.js from npm instead of bower
Sympton onset date
Get rid of syndromes on entry form

If we're using syndromes (and it's still not clear we will) they'd only
be used for querying. Forcing someone to manually categorize the
document is never going to work.
Clean up entry form
District -> Facility
Put patient info on separate form page

We're going to add some more fields
More patient fields

Add patient ID, name, address, and phone number to entry form. All these
fields are mandated by the WHO's guidelines.
Add patient vitals to entry form

The new fields are temperature, pulse, weight, and pre-existing
conditions.
Discharge -> Disposition

Discharged is a type of disposition
Don't send paper trail down to client

It's an infosec accident waiting to happen. Any information you do want
to send to the client, e.g. document creation date, should be saved in a
separate field. The paper trail is designed for forensic analysis only
by someone with access to the cluster.
Record submission date on visits

This duplicates what we already store in the paper trail, but the
`paperTrail` really shouldn't be sent down to the client. Submission
date, on the other hand, is totally safe to send down.
Warn when shifting dates into the future