Increase D&D performances of Blocks with `avoidChildren` option

src/dom_components/model/Component.js

@@ -400,7 +400,7 @@ const Component = Backbone.Model.extend(Styleable).extend(
       // is not visible
       const comps = new Components(null, this.opt);
       comps.parent = this;
-      comps.reset(this.get('components'));
+      !this.opt.avoidChildren && comps.reset(this.get('components'));
       this.set('components', comps);
       return this;
     },

src/utils/Droppable.js

@@ -87,7 +87,7 @@ export default class Droppable {
     // any not empty element
     const content = em.get('dragContent') || '<br>';
     this.sorter.setDropContent(content);
-    this.sorter.startSort(this.el);
+    this.sorter.startSort();
     em.trigger('canvas:dragenter', dt, content);
   }
 

src/utils/Sorter.js

@@ -312,6 +312,7 @@ module.exports = Backbone.View.extend({
       if (!dropModel) {
         let comps = em.get('DomComponents').getComponents();
         let tempModel = comps.add(dropContent, {
+          avoidChildren: 1,
           avoidUpdateStyle: 1,
           temporary: 1
         });