Fixed broken link to install_course.

We also now use url_for, since it is more dynamic and doesn't
require us to change the target url on the template if we change
the endpoint. (It refers to a function for a url, rather than it being
hardcoded)

refs #16251
Documented general.py

refs #16299
Added note for what USER_PERMS are for.

refs #16299
Added some documentation for Form classes.

It may seem a bit redundant, but it will be useful when we auto-generate
docs and have something to describe the classes.

refs #16299
Updated documentation on models.

refs #16299
Added more precise documentation for utils.

refs #16299
Added some documentation for manage.

refs #16299
Added comments to install_course.js

refs #16299
Added some comments for migrate.js

This file should be cleaned up, it looks like a tornado hit it.

refs #16299
Added comments for report.js

refs #16299
Added comments for update_models.js

refs #16299
Merge branch 'bug/16299' into develop
Merge branch 'bug/16251' into develop
Added option to create default user.

refs #16239
Fixed comment.

refs #16239