HDF I/O format

[perrette]

Would be nice to have a HDF I/O format as pandas and larry have. Note that netCDF4 is based on HDF and has advantages on HDF such as the possibility to extract only specific slices of an array (useful for large inputs), but it is not possible to delete a variable in a netCDF dataset, and it requires additional libraries that the standard user may not have. It seems that anaconda and other python distros do have HDF support, so it would make a lot of sense to add that.

Two possibilities:

• use another existing package with already built-in support for HDF5 such as larry or pandas. Requires fixing larry's to/from methods in the first case, and to group/ungroup dimensions in the second case, in order to export as pandas DataFrame with multiindex.
• create a specific DimArray format with pytable.