Refactoring and flexibility changes

* Split game module into game and game_interface
* Move core_lib to corelib
* Move miniwindow to corelib
* Introduce init.lua script for initializing the client, giving much more flexibility
* OTClient is no longer Application derived and is much simpler

modules/corelib/widgets/uibutton.lua

@@ -0,0 +1,7 @@
+UIButton = extends(UIWidget)
+
+function UIButton.create()
+  local button = UIButton.internalCreate()
+  button:setFocusable(false)
+  return button
+end