Removed SDL libraries from project since they assumed the libraries had a specific path.

Furthermore, the SDL.dll is not required for MonoKle to be built, nor is it required for the WindowsDemo to be built & run.

Finally, the SDL.dll is included when setting up a new MonoGame project, thus there is no need for MonoKle to bring it along.
Merge branch 'fix/sdl-lib' into dev