This allows users to set custom CSS classes on aggregations potentially
restyling them differently for different use cases.
This makes startScope and finishScope part of the public API of the
Aggregation class. It should no longer be called within render() but is
instead called outside.
This might potentially break plugins implementing their own
aggregations. Needs to be checked
To avoid confusion with the Lookup type, the three different ways of
accessing a schema have now the following names:
* page data - for revisioned struct data attached to a page
* serial data - for an unrevisioned list of struct data attached to a
page
* global data - for an unrevisioned list of struct data not attached to
any page (formaly known as lookup schema)
The editor mechanism used for serial and global data is now called
AggregationEditor
Some reference to lookup schemas is still in the bureaucracy support
part.
