Backports, 0.2.x - specific changes only

Left some comments on the MR. Course self-sign-ups seem to be broken, there's a couple of ways to approach this and I'm not sure the best route.

Found a bug with membership requests when a learning path has a single class - trivial fix and made a commit for this.

Adding a membership on behalf of a user also seems to have issues.

catch → closed merge request !19

catch → changed the visibility of the branch 3467618-lp_status_started to hidden.

catch → changed the visibility of the branch 3467618-views-operators-visibility to hidden.

catch → changed the visibility of the branch hide-nav-block-on-single-activity to hidden.

catch → changed the visibility of the branch lpstatus-views-data to hidden.

catch → changed the visibility of the branch 3467618-module-form to hidden.

catch → changed the visibility of the branch use-markup-in-availability-msg to hidden.

catch → changed the visibility of the branch lp-warnings-fix to hidden.

catch → changed the visibility of the branch fix-membership-group-type to hidden.

catch → changed the visibility of the branch lp-usage-check-followup to hidden.

catch → changed the visibility of the branch learning-path-take-access to hidden.

catch → changed the visibility of the branch incorrect-roles-element-name to hidden.

catch → changed the visibility of the branch classes-update-fix to hidden.

catch → changed the visibility of the branch 0-2-x-backports to hidden.

catch → changed the visibility of the branch lms-dropdown to hidden.

graber → changed the visibility of the branch 3467618-admin-group-take-access to hidden.

graber → changed the visibility of the branch 3467618-allowed-attempts to hidden.

graber → changed the visibility of the branch 3467618-h5p-unfork to hidden.

graber → changed the visibility of the branch 0.2.x to hidden.