Add a _buildParts method to be callled from _buildMulti*
Add a _buildParts method to be callled from _buildMulti*

rbuffat/Fiona,perrygeo/Fiona,Toblerity/Fiona,Toblerity/Fiona,johanvdw/Fiona,rbuffat/Fiona,sgillies/Fiona,perrygeo/Fiona