partial/parallel read.  
o  Change some of the reader tests to go through moab::Interface 
o  fix bug where ReadHDF5 did not compile if MOAB was configured with
   MPI support but the HDF5 library was not.

The reader test changes will hopefully avoid the need to update these
tests very time the internal reader interface changes.

After trying to document the argument list I had previously defined for
this, I came to the conclusion that it was confusing and a little bit
non-sensical for parallel reads.  The num_parts and part_number arguments,
if speicified, should apply to the whole list of tagged sets, rather than
being associated with a particular tag.  Rather than document a broken
API, I decided to fix it.  

Rather than make the num_parts and part_number arguments be two more
arguments to Reader::load_file, wrap all the arguments related to 
partial reads in a struct and pass that as a poitner to Reader::load_file.
This is a little more complicated, but makes sense to me for this
particular case because the vast majority of readers don't support
partial/parallel reads and therefore need never look at the contents
of the struct.

Most of the modified reader sources were just function signature changes.
The only functional change was in ReadHDF5, which is the only reader that
did anything with two arguments in question.





git-svn-id: https://svn.mcs.anl.gov/repos/ITAPS/MOAB/trunk@3982 6162379e-bd28-0410-9a7d-b7f4dcfcad3c