Standardise use of layouts

# Give layouts the love they deserve
Layouts are awesome. There's currently a layout for article info-blocks, the definition list, but it is only currently being used in the category blog view. That makes me sad.

This PR standardises com_content views by extending the use of the definition list layout to article and featured article views as well. As intended with layouts this improves readability, maintainability and versatility of views as the article info definition list markup exists now only in one place, not three.

## Testing
There should be no observable changes. A useless div that previously existed in the article view is now removed, but that has no affect on rendered views, it was superflous.

## Expected result
An improvement in code readability and maintainability.