add openblas support in FindCBLAS.cmake

[thjashin]

Add several lines in FindCBLAS.cmake so that openblas can be found. Also fix a bug caused by improper use of find_library() in ctypes. According to

"If wrapping a shared library with ctypes, it may be better to determine the shared library name at development time, and hardcode that into the wrapper module instead of using find_library() to locate the library at runtime."

https://docs.python.org/2/library/ctypes.html