dxgitrace: Don't generate stub dxgi/d3d10/d3d10_1/d3d11 DLLs/

Manually copying these DLLs into application directory doesn't work
reliably, as internal dependencies between the respective real
DLLs will end up traced.

I left these stubs just a backup solution, in case DLL injection didn't
work, but the fact is that it is just causing unnecessary confusion.

See issue #277.
Update/improve the Windows installation instructions.