Who needs atomic commits? Here comes the GIGANTIC commit!!!
Hopefully, this is the last commit in the very long series of "Let's break the total internal infrastructure of Palapeli" commits. (To be honest, I doubt.)

Here are the changes:

* Rename libpalapelicore to libpalapelipattern because everything else is moved back to Palapeli application. This is possible because the Pattern class gets a proper interface to the Palapeli game engine.
* The Palapeli::Pattern::slice function is renamed to Palapeli::Pattern::doSlice, because there is now another non-virtual slice function which does some initialisation in the base class.
* The piece positions are now loaded or randomized in the Palapeli::Pattern class.* Move libpalapelipattern to a separate directory. Do only include this folder in API documentation.