change dragging from GUI index to module position index. This is o that we have a reference to the module being moved via the fit service. Otherwise, we would have to hook into the fittingView to get to it's representation of the modules in .mods (which includes the blank, or "rack" modules)
enforce hardpoints DONE
make sure fit recalculates DONE
if dragging to empty slot, simply add to that position
fittingViewto get to it's representation of the modules in.mods(which includes the blank, or "rack" modules)