- should reduce mistakes in refactoring
- gives top level ownership of evaluated_format_properties_ptr to a layout node (#2516)
- not sure ^^ if this actually keeps it in scope enough for rendering?
- moves data transformation functions off of text_symbolizer_properties
Create a group_symbolizer_helper for group placments, and extract some code from
text_symbolizer_helper into a base class to share with group_symbolizer_helper.
Also, move tolerance_iterator into its own header file. Use helper in
process_group_symbolizer to find placement positions.
This includes XML parsing of group symbolizer and related objects and
process_group_symbolizer method in the AGG renderer. This also includes
code to collect group symbolizer indexed columns, create sub features,
and match them to group rules.
