Enable support for static HDF5

 - detect if static HDF5 is used
 - surpress dynamic libsplash for static HDF5
 - add dependency to splash_static
Doc Update and Cleanup

- doc: list external dependencies
- CMakeLists:
  - do not use double IF NOT, invert logic
  - add comment about static hdf5 libs that lack -fPIC on 64bit
    which prevents building a shared libSplash from a static only libhdf5.a
-lhdf5 will ne needed for most cases

Actually there is only one case where one does not need
libhdf5.so: hdf5 was provided as static lib *only* and splash
was build static, too.
Even in the case hdf5 provided both static/shared and splash
build static one will still have to link -lhdf5.
Merge pull request #64 from ComputationalRadiationPhysics/static-hdf5

Enable support for static HDF5