[h5md-user] h5md group

[Pierre de Buyl]

Hello,

For now, the h5md group contains only attributes. This was meant to  
indicate the "metadata" nature of the fields found in there.

However, as it contains only these, we may consider moving them as  
datasets. It makes the rapid exploration of the files with h5ls easier.

This is just a question, not a push from my side.

Pierre