Added private `_title` and `_rect`
Added `Window` source file
Added `_flags` to `Window`
Added `Window` constructor definition
Added `Window` constructor declaration;
Moved `_flag` of `Window` little bit down, to keeps compiler happy
Added `Window::Factory` struct
Added `Game` constructor;
Added `window_factory` to `Game` as factory handler
moved `window_factory` in `Game` to protected section
Added `Game` constructor definitions