add job service to be able to cancel plot requests

pdb-js/src/app/visualization-page/visualization-page.component.html

@@ -67,7 +67,8 @@
      
       <div id="plot-button-bar">
         <button 
-        *ngIf="!enableGallery"
+        *ngIf="!enableGallery && !plotJobActive"
+        [disabled]="plotJobActive"
         mat-button
         matTooltip="Create Plot" 
         (click)="plot()">
@@ -75,7 +76,7 @@
           Plot
         </button>
         <button 
-          *ngIf="enableGallery"
+          *ngIf="enableGallery && !plotJobActive"
           mat-button
           matTooltip="Create Gallery"
           (click)="gallery()"
@@ -83,6 +84,11 @@
           <img src="assets/img/four-squares-line.svg" class="icon-inline" aria-hidden="true" title="Create Gallery (only active if 'Split' is set)" />
           Gallery
         </button>
+        <button 
+          *ngIf="plotJobActive"
+          mat-button
+          (click)="abort()"
+          matTooltip="abort"><img src="assets/img/close.svg" class="icon-inline" /> Abort</button>
       </div>
     </div>
   </div>