Enhancement:- Drag and drop cards on to the battlefield.

I see in Xmage we can drag and reorder our hand around by holding down the mouse button and moving the cards around in our hand area but how about being able to drag and drop cards onto the battlefield to play them as well as click on them?

Start by locating the client code that handles dragging and reordering cards in the hand, then compare it with the existing click action for playing cards onto the battlefield. Done means a card can be dragged from the hand onto the battlefield and produces the same play result as clicking it; verify that the existing hand-reordering behavior still works.

Written by the indexing model from the issue text.