Fix account-deletion dialog

• Solves scrolling problems
• Show sessions as bullet list
• Sort list by session name

Closes #400 (closed), #399 (closed), #398 (closed)

src/app/components/shared/_dialogs/delete-account/delete-account.component.html

@@ -2,9 +2,9 @@
   <h3>{{ 'header.sure' | translate }}</h3>
   <mat-divider></mat-divider>
   <p>{{ 'header.really-delete-account' | translate }}</p>
-  <mat-list *ngFor="let room of rooms; let i = index">
-    <mat-list-item><strong>{{ i + 1 }}:  {{ room.name }}</strong></mat-list-item>
-  </mat-list>
+  <ul *ngFor="let room of rooms">
+    <li>{{ room.name }}</li>
+  </ul>
   <div fxLayout="row" fxLayoutAlign="center" fxLayoutGap="10px">
     <button mat-raised-button class="abort" (click)="close('abort')">
       {{ 'header.abort' | translate }}