make course settings form more accessible

change the course settings form so it's
always a form (similar to the account settings form)
so that way the labels always have referenced elements

test plan:
* using a screenreader, the labels should always reference
the proper input items (rather than labelling nothing
until the "edit" button is clicked)

closes #CNVS-16234

Change-Id: I66d64c5000c6e43291c34536452518ba1dee0945
Reviewed-on: https://gerrit.instructure.com/43091
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Nathan Rogowski <nathan@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Cosme Salazar <cosme@instructure.com>