TCR fixes 2 (#2286)

* prevent default on dragover in dropHint, to allow drop event to fire

* add notebook snapshot to preview

* fix for preview image overlay

* pin fast-sass-loader version to 1.4.6

* fix saveAs in plot image export

* fix elements search in inspector

* fix current Search error

* fix anonymous render error in layout

* navigate and edit on create

* remove domainObjects from composition when deleting frames and containers, and also fix a bug whereby a user can add domainObject via drag and drop(composition) but because of the lack of containers, it will not be added to the flexible layout

* fix index undefined error when reordering containers

* throw an error when user cancels instead of returning false

* fixes for toolbar not updating on selection change

* fix errors when objects without context are returned by the search aggregator

* prompt user before cancelling edit

* check transactions before prompting user

* add save and continue editing option to save menu

* prompt user if in edit mode and is navigating away

src/plugins/flexibleLayout/flexibleLayoutViewProvider.js

@@ -57,7 +57,7 @@ define([
                                 layoutObject: domainObject
                             },
                             el: element,
-                            template: '<flexible-layout-component ref="flexibleLayout"></flexible-layout-component>'
+                            template: '<flexible-layout-component ref="flexibleLayout" :isEditing="isEditing"></flexible-layout-component>'
                         });
                     },
                     getSelectionContext: function () {