Goal:

- Create a library that can open a Vulkan-ready window with a single call to a function.
- Interchangeable with fssimplewindow library, which creates an OpenGL-ready window.
- Source code will reside under fssimplewindow directory so that common sources are not duplicated.
- Isolate OpenGL part and Vulkan part from fssimplewindow source files and create separate CMakeLists.txt for fssimplewindow and fsvulkanwindow libraries.
