hdf5 equivalent of config_dumper
we need to have some kind of metadata in the hdf5 files.
(normal tuples also don't have art metadata, so need it for them as well)
working on a header-only reader- has a specialized exception ERS package that may introduce more dependence than we want.
Working on channel map.
Compression out of the daq - do it on SSD? Cost estimate? LDRD