[player] Init elements of hidden section on start

Use "display:none" instead of "*ngIf" to hide the section and make sure
its children are loaded.

projects/player/src/app/components/section-container/section-container.component.html

-<aspect-section *ngIf="isVisible"
-                class="section"
+<aspect-section [class]="isVisible ? 'section' : 'hidden-section'"
                 [class.static-section]="!section.dynamicPositioning"
                 [style.backgroundColor]="section.dynamicPositioning ? null : section.backgroundColor"
                 [style.minHeight]="section.dynamicPositioning ? 'auto' : section.height + 'px'"

projects/player/src/app/components/section-container/section-container.component.scss

@@ -5,6 +5,10 @@
   z-index: 0;
 }
 
+.hidden-section{
+  display: none;
+}
+
 .static-section{
   display: block;
 }