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
Should be running clean now, thanks to your rebase help.  Got my "always do" commands down pat after rebasing a pile of branches.