Adding cmake module to find various bits of the DirectX SDK from Microsoft

File originally obtained from game kit @ https://gamekit.googlecode.com/svn-history/r841/trunk/CMake/Packages/FindDirectX.cmake
Merge branch 'feature/optional-build-directx-samples' into merge-test

* feature/optional-build-directx-samples:
  Adding cmake module to find various bits of the DirectX SDK from Microsoft