Add options to show role and/or category in contributor field formatter.

Also it should show some default values for role or category if any of them is not set. This is possible that role or category are not set when reference entity is created via import process. Furthermore widget doesn't allow "empty" value so when user arrives to reference edit form and this reference have any of role or category is not set in entity, one actually sees default values in widget and may think that they're both set on entity, but on view they will not be shown. This may be confusing.