Add checkbox to skip backup

src/views/settings.html

@@ -28,6 +28,10 @@
                 </div>
             </div>
             <div class="modal-footer">
+                <label class="checkbox-inline pull-left">
+                    <input type="checkbox" ng-model="update.skipBackup"><b>Skip backup</b>
+                </label>
+
                 <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                 <button type="button" class="btn btn-success" ng-click="update.startUpdate()" ng-disabled="update.busy" ng-show="(installedApps | readyToUpdate)"><i class="fa fa-circle-notch fa-spin" ng-show="update.busy"></i> Update</button>
             </div>