SUMMARY
RSS feeds may contain additional metadata using the namespace extensions.
Let the user specify such fields and add them to the Feed Widget as columns

DETAILS
The syndication library lets us access unhandled elements.
In the feed widget, we can have a button "Add Column" opening a dialog with fields for:
  - Column Title
  - RSS Field
  - Value type
This should allow the user to define at least simple value fields.
When the user confirms the dialog, an additional column should pop up in the Feed-Items View according to the user provided parameters.

* Bonus if we can add a simple way of accessing hierarchical values
* Bonus if we can display a real time visualisation using data from the RSS feed, ass the user is typing the selection