New build standards on Windows

Rationalize the build system on Windows.  This update defines the official h5py CMake settings file for building HDF5 for redistribution, and corrects the build directories in setup.py to use those generated by CPack, as opposed to the current ad-hoc system.

A new naming convention for the dlls is also introduced; we continue to rename the HDF5 dlls to avoid run-time conflicts with PyTables and others.  CMake is used to prefix the DLL names with `h5py_`, as opposed to the old approach of manually editing the solution files.

Also added a brief README in the `windows` folder to get people started.