Prepare the move of material science specific data classes to separate plugin

[sphuber]

Over time, domain specific calculation and data classes have already been moved to individual repositories. There are a few remaining that we may want to move to e.g. aiida-materials-science. Decide which one of these to move and where:

• array.bands -> aiida-atomistic
• array.kpoints -> aiida-atomistic
• array.projection -> aiida-atomistic
• array.trajectory -> aiida-atomistic
• cif -> aiida-atomistic
• orbital -> aiida-atomistic
• structure -> aiida-atomistic
• upf -> aiida-pseudo

The same goes for any related tools in aiida.tools.data.
Potential name for the new plugin:

• aiida-solid-state
• aiida-atomistic
• aiida-materials-science
• aiida-matsci

EDIT: after discussion during the December 2021 coding week it has been decided to move all plugins mentioned above to a new plugin package called aiida-atomistic, with the exception of UpfData which is already replaced in aiida-pseudo. See also this AEP that will discuss the details of how the move will be implemented.

[sphuber]

Questions:

• What to do with the importers, which import mostly UpfData or CifData?
• What to do with the resources and translators for these data types in REST API

[sphuber]

After discussion it is agreed that this is too big of a change after v1.0.0b2 and just before v1.0.0. So this will have to be postponed to v2.0.0

[csadorf]

Since this is not going into the next release, should we remove the priority/critical-blocking label?

[giovannipizzi]

Done

[giovannipizzi]

I vote for removing this from 2.0 if we want to release it in the next few months, as it's not clear if the amount of effort needed to make this move properly is worth the resulting advantages we would get

[sphuber]

I think we indeed decided to not include this in v2.0 due to lack of time necessary for the preparation. So I am removing the milestone.