allow to upload files from the ckeditor

while here:
- update ckeditor to 4.21.0
- add a Sourcedialog plugin to the ckeditor

winixd/html/fun_upload.html

@@ -160,7 +160,7 @@
               <td>
                   <span class="preview">
                       \{% if (file.thumbnailUrl) \{ %\}
-                          <a href="\{%=file.url%\}" title="\{%=file.name%\}" download="\{%=file.name%\}" data-gallery><img src="\{%=file.thumbnailUrl%\}"></a>
+                          <a href="\{%=file.url%\}" title="\{%=file.name%\}" download="\{%=file.name%\}" data-gallery><img style="max-height: 150px;" src="\{%=file.thumbnailUrl%\}"></a>
                       \{% \} %\}
                   </span>
               </td>