[ADF-1115] selection management for DT/DL components (#2100)

* row select/unselect dom events for DT

- new events for datatable
- improved unit tests for empty content placeholders

* improved selection management for DT

* selection management for document list

* fix tests

ng2-components/ng2-alfresco-datatable/src/directives/loading-template.directive.ts

@@ -30,7 +30,9 @@ export class LoadingContentTemplateDirective implements AfterContentInit {
     }
 
     ngAfterContentInit() {
-        this.dataTable.loadingTemplate = this.template;
+        if (this.dataTable) {
+            this.dataTable.loadingTemplate = this.template;
+        }
     }
 
 }