improved uploading of files (#1730)

* improved uploading of files

- new core/UploadDirective to allow dropping files to any html element
- enhanced file dropping for DataTable rows (disabled by default)
- enhanced file dropping for DocumentList rows (disabled by default)
- upload drop area now handles file uploads for child elements (i.e.
rows in the document list)

* fix unit tests

* unit tests and code cleanup

* #1732, fix upload of folders

ng2-components/ng2-alfresco-documentlist/src/components/document-list.component.ts

@@ -82,6 +82,9 @@ export class DocumentListComponent implements OnInit, OnChanges, AfterContentIni
     @Input()
     emptyFolderImageUrl: string = this.baseComponentPath + 'assets/images/empty_doc_lib.svg';
 
+    @Input()
+    allowDropFiles: boolean = false;
+
     skipCount: number = 0;
 
     pagination: Pagination;