Remove the Level Inspector from Prefab mode and move behavior to Entity Inspector. (#149)

* Remove Level Inspector from Prefab mode, and integrate the same behavior in the Entity Inspector

* Show prefab name in level entity row of the Outliner. Allow Ui Handlers to prevent renaming.

* Separate setting the prefab's template path and the container entity name.

* Disable reparenting to root level

* Disable the ability to rename the level entity.

* Fixes as per Ram's review

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabSystemComponent.cpp

@@ -121,6 +121,7 @@ namespace AzToolsFramework
             }
 
             newInstance->SetTemplateSourcePath(relativeFilePath);
+            newInstance->SetContainerEntityName(relativeFilePath.Stem().Native());
 
             TemplateId newTemplateId = CreateTemplateFromInstance(*newInstance);
             if (newTemplateId == InvalidTemplateId)