scivision/h5fortran: bugfix/feature for chunked sets

added methods

%exist('/foo', ierr) does a variable exist in the file

%is_contig('/foo', ierr) is the variable contiguous (not chunked, not compressed)

%is_chunked('/foo', ierr) is the variable chunked (may or may not be compressed)

bugfix from 2.4.0, accidentally making compression disabled. Added tests to avoid this happening again.