Create calcfunctions for potential file modification

[JPchico]

Right now the potential is very rigid, but there should be a series of calcfunctions to deal with making the potential magnetic, changing shapes (for slabs and situations like this). This calcfunction needs to be called at the workchain level if necessary.

This function needs to be modified to work with the new potential data
https://github.com/JPchico/aiida-kkr/blob/develop_base_restart_workchains/aiida_kkr/tools/common_workfunctions.py#L932:L1105