settings: Add "View file" option over file name.

The "View file" option will open the file in a new window if it
is a filetype that can open in the browser and if not, it will just
trigger a download or whatever the browser's settings are.

static/templates/uploaded_files_list.handlebars

@@ -1,6 +1,10 @@
 {{#with attachment}}
 <tr class="uploaded_file_row" id="{{name}}">
-    <td>{{ name }}</td>
+    <td>
+        <a type="submit" href="/user_uploads/{{path_id}}" target="_blank" title="{{t 'View file' }}">
+            {{ name }}
+        </a>
+    </td>
     <td>{{ create_time }}</td>
     <td>
         {{#if messages }}