gui: Add confirmation on removing devices and folders (fixes #4543)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4563
LGTM: calmh

gui/default/syncthing/device/editDeviceModalView.html

@@ -87,7 +87,7 @@
       <button type="button" class="btn btn-warning btn-sm disabled" ng-if="willBeReintroducedBy" tooltip data-original-title="This device will be reintroduced by {{ willBeReintroducedBy }}">
         <span class="fa fa-minus-circle"></span>&nbsp;<span translate>Remove</span>
       </button>
-      <button type="button" class="btn btn-warning btn-sm" ng-click="deleteDevice()" ng-if="!willBeReintroducedBy">
+      <button type="button" class="btn btn-warning btn-sm" data-toggle="modal" data-target="#remove-device-confirmation" ng-if="!willBeReintroducedBy">
         <span class="fa fa-minus-circle"></span>&nbsp;<span translate>Remove</span>
       </button>
     </div>