h5extract extract everything

A common use case for h5extract will be this:

h5extract --offline-header --event-info --offline-hits --mc-hits --mc-tracks --mc-tracks-usr-data --reco-tracks filename.root

aka extract everything. It is quite lengthy and prone to errors. I propose to make this the default behaviour, i.e. when the user calls h5extract filename.root, it should extract everything.

Alternatively we could use some kind of special flag, e.g. h5extract --all.

What do you think?