Adding viewname to menuitems manager

The "Menu Manager: Menu Items" view currently shows the "Menu Item Type" as 
> "component" » "layout"

This commit will add the viewname to it as set in the metadata.xml:
> "component" » "view" » "layout"

Interesting enough the code currently requires the file present and this title set, but doesn't use it. So it's probably just an oversight.

This commit will also use the "message" set in the metadata.xml as fallback for the item type description if there is no "message" set in the layout file.