SSP-2758 Fix malformed report CSV output

Fixed reports:

  - Disability
  - Journal
  - All MAP reports

Also renamed the Number of Courses in Plan report to Number of Plans
By Course and adjusted report title and column headers accordingly.

Because the Number of Students by Status report involves a nested
report model, this patch includes an API change to
AbstractCsvWriterHelper which impacted several other reports as well
as our caseload export mechanism.