#152 Support for custom 'empty folder' template

- default background image for empty folders
- support for user-defined custom templates
- readme updated

demo-shell-ng2/app/components/files/files.component.html

@@ -9,6 +9,13 @@
             [breadcrumb]="breadcrumb"
             (itemClick)="showFile($event)"
             (folderChange)="onFolderChanged($event)">
+        <!--
+        <empty-folder-content>
+            <template>
+                <h1>Sorry, no content here</h1>
+            </template>
+        </empty-folder-content>
+        -->
         <content-columns>
             <content-column source="$thumbnail"></content-column>
             <content-column
@@ -136,4 +143,4 @@
 <alfresco-viewer [(showViewer)]="fileShowed" [urlFile]="urlFile" [overlayMode]="true">
     <div class="mdl-spinner mdl-js-spinner is-active"></div>
 </alfresco-viewer>
-<file-uploading-dialog></file-uploading-dialog>
+<file-uploading-dialog></file-uploading-dialog>