Changed user enrolment to set default section

If section ends in "00" (e.g. D100, E100, G300) or if only 1 section in the course (i.e. no section tutorials) then enrol teacher to that section.
Merge remote-tracking branch 'upstream/sfu-develop' into course-form-plugin
Hide Sandbox course option if one already exists for the user

Added JSON call to get sandbox info if exists.
Fixed typo in variable name
Minor text edits on form and confirmation page
Changed title of form to match Canvas button and the original course form
Merge pull request #22 from ronvs/course-form-plugin

Course form plugin