HDF5 needs some extra functionality

Created by: anjos

This ticket keeps track of the extra functionaliy needed on io::HDF5File to make it more flexible before a full release:

1. Ability to save and distinguish boolean files
2. Ability to save scalar values (simple and arrays)
3. Ability to save single strings and string lists
4. It would be nice to have attribute support as well
5. Implement meat of the HDF5File::copy() method