rewrite plotwidget to use new system
rewrite plotwidget to use new system

michaelaye/vispy,drufat/vispy,drufat/vispy,michaelaye/vispy,drufat/vispy,ghisvail/vispy,michaelaye/vispy,Eric89GXL/vispy,ghisvail/vispy,Eric89GXL/vispy,Eric89GXL/vispy,ghisvail/vispy