hdf5 support

Hello Robert and Balint,

this is a pull request for including my QDP++ HDF5-Implementation into the QDP++ repo. I have added some datatypes such as (Lattice)Baryonblocks, which might also be useful for other people. However, it does not hurt if they are inside the repo. I also modified the autoconf and automake files such that they recognize --enable-hdf5 and --with-hdf5=<HDF5_INSTALL_DIR>.

I further added a function which returns the local node coordinate from the lexicographic coordinate, this I needed for my FFT. The wrapper for  FFTW is not implemented into QDP++ (yet), and rather external, but I can hook it in if you like.

Best
Thorsten