Changing how creating UGDK executables work.

There's a new macro in the main UGDK CMakeLists called add_ugdk_executable that creates that given the target name and the sources, creates the executable and links it to UGDK.
However, in the case of an android build, that macro creates a shared lib and adds the extra source file that provides the necessary JNI hook.
Also, the examples have more meaningful names and should all be shared between desktop and android.
Mouse events now contain the mouse position.
desktop::Window now extracts information from the window.
Make the android main not depend on SDL.
Finish draggable-box example.