LPS-33636 indicate portlet-column as dropzones once portlets are dragged

Hi Nate, I'd like to see this functionality in the portal - I see inexperienced users in training frequently struggling with the lack of visual feedback on where to drop portlets.
The design - if you can call it design - may be changed any way more suitable: I'm able to make things look different, others (you) will be able to make it look nice.