message: change from ng-container to div to stabilize drag and drop
diff: <div class="users" *ngIf="fuzzySearch.length > 0">
  <p><b>In course ({{usersInCourse.length}})</b></p>
  <md-list class="drop" [dragula]='dragulaBagId' [dragulaModel]='usersInCourse'>
  - <ng-container *ngFor="let member of usersInCourse">
  + <div *ngFor="let member of usersInCourse">
  <md-list-item class="list" *ngIf="fuzzysearch(fuzzySearch,member)" [attr.data-id]="[member._id]">
  <i class="material-icons md-48">drag_handle</i>
  <span class="listBg" [grav]="member.email"></span>
  <span class="uid">{{member.uid}}</span>
  <span class="email">{{member.email}}</span>
  </md-list-item>
  - </ng-container>
  + </div>
  </md-list>
  <p><b>Not in course ({{users.length}})</b></p>
  <md-list class="drop" [dragula]='dragulaBagId' [dragulaModel]='users'>
  - <ng-container *ngFor="let user of users">
  + <div *ngFor="let user of users">
  <md-list-item class="list" *ngIf="fuzzysearch(fuzzySearch,user)" [attr.data-id]="[user._id]">
  <i class="material-icons md-48">drag_handle</i>
  <span class="listBg" [grav]="user.email"></span>
  <span class="uid">{{user.uid}}</span>
  <span class="email">{{user.email}}</span>
  </md-list-item>
  - </ng-container>
  + </div>
  </md-list>
  </div>
  