test packing modes and shipping costs on variations

[ ] packed together - variations can have different weights, check these are reflected in shipping costs
[ ] packed separately - additional container - variations can have different weights, check these are reflected in shipping costs
[ ] packed separately - no additional container - hide the virtual checkbox AND the shipping settings at the variation level
[ ] virtual - hide the virtual checkbox AND the shipping settings at the variation level

kathyisawesome / wc-mnm-variable