Added copying of cell's layer properties to the draggable view

[bkryza]

Hi,

I had a small problem with cells which had nonzero corner radius and shadow as well as some scale transform (e.g. on selected cells). The properties were not copied to the draggable preview image view and it looked strange.

I've added a simple fix which copies main layer attributes from the cell view to the draggable preview and also calculates the preview frame based on the bounds property (and adjusts the center) which works even when the original cell has some scale transform.

Cheers,
Bartosz

[jeffdav]

I had a similar problem (I had specific requirements for visual adjustments to the draggable preview image) that I solved by adding some delegate methods. See my pull request (#60). I think it solves the problem in a more generic way.