Feature/sa add template fields

[ChemiKyle]

Adds date of birth and age at enrollment fields, the latter being hidden and calculated from date of birth and onstudydate. Age at enrollment is sent with SA data, but not date of birth.

Also makes race multi selectable. Backend is updated to condense multiple selections for race into "More than one race" (the coded value, "08", is not yet recognized by the API). This backend update should be compatible with either a checkbox or radio option for race.

Note that the introduction of checkboxes for race mean that the R script for simulation may need to be updated as checkboxes are stored in the database as multiple rows with the same field_name.

I realized too late that a previous commit added these fields to the template, my variable names are not the same. This should not affect the backend, however.

[pbchase]

@ChemiKyle, I am happy with your commits. please merge if you are happy with mine.

[ChemiKyle]

There's still a 503 error at our testing endpoint, but since we know this is the cause of the error I'm going to merge.