- some refactoring (publish_status_clause)
- new value for form_constraints: @table_properties
  to specifies values for form-usages and count_usages.
  example
      @table_properties:publish_status=all
  to list/count all usages, independent of publish status
- improve method view for FormPages based on pure form
  rendering (use sanity checks, ensure the margin-form class)