Move registerLocaleData from SliderComponent to AppComponent

registerLocaleData is needed to set the thousands' separator. It has called once per application and should not stay in SliderComponent (although no other component need this by now).

projects/common/ui-elements/slider/slider-element.ts

-import localeDe from '@angular/common/locales/de';
-import { registerLocaleData } from '@angular/common';
 import {
   FontElement,
   FontProperties,
@@ -22,7 +20,6 @@ export class SliderElement extends InputElement implements FontElement, SurfaceE
 
   constructor(serializedElement: UIElement) {
     super(serializedElement);
-    registerLocaleData(localeDe); // todo MOVE!
     Object.assign(this, serializedElement);
     this.positionProps = initPositionedElement(serializedElement);
     this.fontProps = initFontElement(serializedElement);

projects/editor/src/app/app.component.ts

 import { Component, OnInit } from '@angular/core';
 import { TranslateService } from '@ngx-translate/core';
+import { registerLocaleData } from '@angular/common';
+import localeDe from '@angular/common/locales/de';
 import { VeronaAPIService } from './services/verona-api.service';
 import { UnitService } from './services/unit.service';
 
@@ -37,5 +39,6 @@ export class AppComponent implements OnInit {
       });
 
     this.veronaApiService.sendVoeReadyNotification();
+    registerLocaleData(localeDe);
   }
 }

projects/player/src/app/app.component.ts

 import { Component, OnInit } from '@angular/core';
 import { TranslateService } from '@ngx-translate/core';
 import { MatDialog } from '@angular/material/dialog';
+import { registerLocaleData } from '@angular/common';
+import localeDe from '@angular/common/locales/de';
 import {
   Unit
 } from '../../../common/models/unit';
@@ -42,6 +44,7 @@ export class AppComponent implements OnInit {
     this.veronaPostService.sendVopReadyNotification(this.metaDataService.playerMetadata);
     this.translateService.addLangs(['de']);
     this.translateService.setDefaultLang('de');
+    registerLocaleData(localeDe);
   }
 
   private initSubscriptions(): void {