[ADF-643] upload enhancements (#1949)

* rework folder uploading

- flatterns hierarchy on folder upload
- performs a single traversal for the entire folder heirarchy and ends with a comple file list
- allows now dropping folders on existing folders
- overall code improvements

* fix unit tests

* readme updates

* clean old and unused code

* code cleanup

* limit concurrent uploads

* update code as per review

* fix upload button for Safari

* fixes for Safari

- Safari compatibility
- code updates based on review

* fix code

* fix unit tests

ng2-components/ng2-alfresco-upload/src/directives/file-draggable.directive.ts

@@ -16,6 +16,7 @@
  */
 
 import { Directive, EventEmitter, Input, Output, OnInit, OnDestroy, ElementRef, NgZone } from '@angular/core';
+import { FileUtils } from 'ng2-alfresco-core';
 
 @Directive({
     selector: '[file-draggable]'
@@ -28,7 +29,7 @@ export class FileDraggableDirective implements OnInit, OnDestroy {
     enabled: boolean = true;
 
     @Output()
-    onFilesDropped: EventEmitter<any> = new EventEmitter();
+    onFilesDropped: EventEmitter<File[]> = new EventEmitter<File[]>();
 
     @Output()
     onFilesEntityDropped: EventEmitter<any> = new EventEmitter();
@@ -73,16 +74,20 @@ export class FileDraggableDirective implements OnInit, OnDestroy {
                     if (typeof items[i].webkitGetAsEntry !== 'undefined') {
                         let item = items[i].webkitGetAsEntry();
                         if (item) {
-                            this.traverseFileTree(item);
+                            if (item.isFile) {
+                                this.onFilesEntityDropped.emit(item);
+                            } else if (item.isDirectory) {
+                                this.onFolderEntityDropped.emit(item);
+                            }
                         }
                     } else {
-                        let files = event.dataTransfer.files;
+                        let files = FileUtils.toFileArray(event.dataTransfer.files);
                         this.onFilesDropped.emit(files);
                     }
                 }
             } else {
                 // safari or FF
-                let files = event.dataTransfer.files;
+                let files = FileUtils.toFileArray(event.dataTransfer.files);
                 this.onFilesDropped.emit(files);
             }
 
@@ -90,22 +95,6 @@ export class FileDraggableDirective implements OnInit, OnDestroy {
         }
     }
 
-    /**
-     * Travers all the files and folders, and emit an event for each file or directory.
-     *
-     * @param {Object} item - can contains files or folders.
-     */
-    private traverseFileTree(item: any): void {
-        if (item.isFile) {
-            let self = this;
-            self.onFilesEntityDropped.emit(item);
-        } else {
-            if (item.isDirectory) {
-                this.onFolderEntityDropped.emit(item);
-            }
-        }
-    }
-
     /**
      * Change the style of the drag area when a file drag in.
      *