[Frontend] Label context arrows now always visible

open #929
- Also enable frame dragging in title area when
editing in Layout;
- CSS and markup changes;

platform/commonUI/browse/res/templates/browse/object-header.html

@@ -26,5 +26,5 @@
     <mct-representation
         key="'menu-arrow'"
         mct-object='domainObject'
-        class="flex-elem"></mct-representation>
+        class="flex-elem context-available-w"></mct-representation>
 </span>