Add comment field to Role table

This change adds a comment/description field for Roles to allow
administrators to remind themselves what a specific role designates.
Add comment to list of fields saved from admin UI

Add missing file from previous check-in to correctly expose comment
field to save/fetch from the admin UI.
Clean up rendering of main admin page

Use HTML instead of repeated `echo` commands.

Also use a class instead of a raw style for the button areas.