A pyfive "ncdump"

[bnlawrence]

One of our objectives with pyfive is to avoid having to have a C-library hanging around where we have our pure-python. In that context it would be nice to include a lightweight equivalent of h5dump or ncdump.

For a developer, h5dump gives more deep information, but in most cases where we have dveelopers, we do have the c-library, so I am tempted to suggest we mimic functionality a bit more like ncdump (though of course we could do both).

Anyway, this proposed enhancement is to deliver something which has the functionality of ncdump, that is, it identifies dimensions and variables and provides key attribute information.

In building a prototype for this functionality I realised we have a problem with being a bit too aggressive in the b-tree caching. More on that in another issue.

[kmuehlbauer]

I'd suggest to have p5dump which drops in for h5dump and over at h5netcdf we should have the according h5dump (name tbd). See also h5netcdf/h5netcdf#144.