* Make InputHandler own the key cache
* Add a helper function InputHandler::cancelPressed to avoid multiple similar calls in game.cpp
* Move RandomInputHandler::step definition into cpp file
* Various code style fixes
* Use range based for loops
* Use empty instead of empty objects
* Use C++11 default keyword for trivial constructors and destructors
* Drop some useless casts
* Use emplace_back instead of push_back to improve performance of some vectors push
* Move KeyList & InputHandler from game.h to client/inputhandler.h
We have a header for inputs, move inputhandler class & related keylist object to it
Also introduce a cpp file for MyEventReceiver::OnEvent function in inputhandler.h because a so huge function doesn't needs to be inlined
* Pass clang-format on inputhandler.{cpp,h} (compatible)
