* The maximum of users to be displayed raised from 30 to 100. This is
consistent with the legacy users selector available via enrolment
methods page.
* If there are more users found matching the search criteria, notify the
user instead of displaying them. This is to prevent false impression
that there are only that many users.
* Added behat tests for the new behaviour.
The add/roles thing was only converted to bootstrap 2/4 markup and the yui left in place.
The modal for adding users to a course was unsavable so I rewrote it with an mform in a popup, still calling
the same (barely) modified ajax script.
The webservice for searching cohorts was taken from admin/tool/lp and moved into /cohort. I added a generic "cohort"
mform element at the same time.
The webservice for searching for users was taken from the original ajax script.
