collapsable ext sections, fix ext menu scroll issue

app/assets/stylesheets/app/_extensions.scss

@@ -38,6 +38,8 @@
   padding-top: 12px;
   padding-left: 10px;
   padding-bottom: 10px;
+  cursor: pointer;
+  user-select: none;
 
 
   > .title {
@@ -63,7 +65,7 @@
 
 .dropdown-menu.editor-menu {
   overflow-y: scroll;
-  max-height: 85vh;
+  max-height: calc(85vh - 90px);
 
   &:not(:first-child) {
     margin-top: 18px;

app/assets/templates/frontend/directives/contextual-menu.html.haml

@@ -1,12 +1,12 @@
 %ul.dropdown-menu.dropdown-menu-left.nt-dropdown-menu.dark.editor-menu
   .extension{"ng-repeat" => "extension in extensions"}
-    .menu-section-header
+    .menu-section-header.pointer{"ng-click" => "extension.hide = !extension.hide"}
       .title {{extension.name}}
       .subtitle
         Can access your data
         %strong {{accessTypeForExtension(extension)}}
       .spinner.loading{"ng-if" => "extension.loading"}
-    %ul
+    %ul{"ng-if" => "!extension.hide"}
       %li.menu-item{"ng-repeat" => "action in extension.actionsWithContextForItem(item)", "ng-click" => "executeAction(action, extension)"}
         .menu-item-title {{action.label}}
         .menu-item-subtitle {{action.desc}}