[editor] Show element type and ID above the properties tabs

This helps identifying the selected element.

projects/editor/src/app/components/unit-view/page-view/properties-panel/element-properties-panel.component.html

 <div *ngIf="selectedElements.length > 0"
      class="properties-panel"
      fxLayout="column" fxLayoutAlign="space-between stretch">
+  <div class="panel-title" fxLayout="column">
+    <ng-container *ngIf="combinedProperties.type">
+      {{'toolbox.' + combinedProperties.type | translate}}
+      <span>{{combinedProperties.id}}</span>
+    </ng-container>
+    <ng-container *ngIf="!combinedProperties.type">
+      <i>Mehrfachauswahl</i>
+    </ng-container>
+  </div>
+  <mat-divider [style.margin-bottom]="0"></mat-divider>
   <mat-tab-group mat-stretch-tabs>
     <mat-tab>
       <ng-template mat-tab-label>

projects/editor/src/app/components/unit-view/page-view/properties-panel/element-properties-panel.component.ts

@@ -23,7 +23,9 @@ import { LikertColumn, LikertRow } from '../../../../../../../common/interfaces/
     'mat-divider {margin: 20px; border-top-width: 9px; border-top-style: dotted;}',
     '.properties-panel {height: 100%; padding-bottom: 20px}',
     '.properties-panel .mat-tab-group {height: 100%; overflow: auto}',
-    ':host ::ng-deep .mat-tab-body-wrapper {height: 100%}'
+    ':host ::ng-deep .mat-tab-body-wrapper {height: 100%}',
+    '.panel-title {font-size: x-large; text-align: center;}',
+    '.panel-title span {font-size: medium;}'
   ]
 })
 export class ElementPropertiesPanelComponent implements OnInit, OnDestroy {