CMake for assimp_view: copy dlls from assimp build over to output folder.
CMake for assimp_cmd: also copy over assimp output binary as PRE_BUILD event.
CMake: use copy_if_different instead of copy and only run PRE_BUILD on Windows as it is not required on *nix anyway.
Merge pull request #89 from assimp/cmake-fixes

CMake Fixes