piecharts.py: allow wedges/wedge labels to be invisible
piecharts.py: allow wedges/wedge labels to be invisible

makinacorpus/reportlab-ecomobile,makinacorpus/reportlab-ecomobile,makinacorpus/reportlab-ecomobile,makinacorpus/reportlab-ecomobile,makinacorpus/reportlab-ecomobile