HDF5/ADIOS: Attribute Write Functor/Read Functors

[ax3l]

@Flamefire introduced in #1410 some functors to HDF5/ADIOS that can be used to verify & read attributes.

To remove code duplication, other read/writes such as sim_slides should be done through it, too.

Please wait for #1430 to be merged before continuing to avoid conflicts.

[BrianMarre]

@psychocoderHPC is this issue still relevant?

[PrometheusPi]

This is not done, but quite useful. @psychocoderHPC what do you think: should we continue this, close (since it is really old) or restart from scratch?

[psychocoderHPC]

I do not understand what this issue is asking for or what feature it suggest.