[CMake] Shared library OutputFile path for Visual Studio

[Neal Meyer]

Is there any particular reasoning why for a shared library project the
.dll file is created in the LibraryOutputPath rather then the
ExecutableOutputPath.  The Import library(.lib) should be placed in
the LibraryOutputPath, but it doesn't make any sense for the .dll to
be placed there as well.

I end up having to copy the .dll output with a post-build step, which
works but is complete a waste of time and just makes the cmake file
more complex for what seems like a very simple case.

-Neal