Removed theme options for cards.

The ability to theme cards dynamically at runtime is being removed. The reason for this is that themes are set when created and seemingly require the recreation of the component to take effect.

Added a check for whether the views are in edit mode before attempting to fetch attributes / resources. This means that the views can be displayed in the UI designer instead of throwing an exception and preventing the developer from being able to effectively use the preview.

Removed erroneous addition of a listener that took place in card thumbnails.