The group concatenation types now consistently sort the returned values
and support aggregating columns containing multiple fields and those
with defined callbacks.
The column class encapsulates all data related to a report column. It
allows developers to define the type of data contained within it, in
addition to how that data is retrieved and formatted for users.
Report actions are used to define action elements that are added to
each report row. They define an icon and link, and can be used to
direct users to related pages according to the current row data.
