Implement distinct appearance of areas I cannot edit

A quick win for gaining a better overview of areas and bars is to reduce the visual significance of the edit bars of areas, which I cannot edit.

Areas, which I cannot edit:

• I cannot change the number or arrangement of the contained elements
• they have no dialog attached or
• I lack the necessary rights to open the dialog and change the values it contains

The attached mockup uses a reduced bar for non-editable area, combining a combination of thick border with a flag-like label containing the area name.

I see the following options:

• Option 1: show a normal area edit bar for all areas, editable or not (forget about this issue)
• Option 2: show a reduced bar for any non-editable area
• Option 3: show a reduced bar for top-level, non-editable areas only
• Option 4: don't show an area edit bar for non-editable areas

Option 4 is probably closest to how Magnolia currently works. I'd prefer to go with option 2 or 3. I would advise against using option 1 (it's how I think 4.5 Sprint III works), since it introduces many bars I actually don't care about - I'd rather use bars for actually editable elements only. But I'd prefer to still mark non-editable areas with reduced bars in order to reveal and document the page structure and ease orienting oneself.