backups: remove the preserve label and add tooltip

src/views/backups.html

@@ -56,10 +56,11 @@
           </div>
 
           <div class="form-group">
-            <label class="control-label" for="inputBackupLabel">{{ 'backups.backupEdit.preserved.label' | tr }}</label>
             <div class="checkbox">
               <label>
                 <input type="checkbox" ng-model="editBackup.persist">{{ 'backups.backupEdit.preserved.description' | tr }}</input>
+
+                <sup><a popover-placement="top-right" popover-trigger="outsideClick" uib-popover="{{ 'backups.backupEdit.preserved.tooltip' | tr: { appsLength: editBackup.backup.contents.length} }}"><i class="fa fa-question-circle"></i></a></sup>
               </label>
             </div>
           </div>