Move the custom multiple step move logic from Freecell to DealerScene.

* Coolo wants to add similar functionality to Forty & Eight, so there
was a desire to abstract the existing Freecell code.

* Moving the code into DealerScene allowed for simpler implementations
in a couple areas.

* While the algorithm used should be unchanged, the code has been
almost completely rewritten and in many cases simplified. The new
implementation is probably less efficient than the previous one
(mostly do to more QList copying) but I think the improved
readability and maintainability are worth it.

* The code now has approximately 1000000% more comments.