Re-factor "billing note"

Exchanging `patient_data.genericval2` for `patient_data.billing_note`
throughout the code base.  Also adding some Billing Report, 837, 835,
270, 271, and dated reminders fixes and tweaks.
Promoting discussion of removing the "generic" and "user" fields from
database.sql
Don't think this should be in the pull request, not clear that it's for "everyone"