Interaction layer specific settings

[LarsSchaaf]

This commit allows for the cutoff and correlation order to be different for different message passing layers.

correlation and r_max now accepts a list of length num_interactions.

eg.

--num_interactions=3
--correlation="[3,3,1]"
--r_max="[7.0,3.0,7.0]"

[ilyes319]

@LarsSchaaf What do you think is needed for the clean up before merging this?

[davkovacs]

Should we implement as part of tis PR the central atom dependent cutoff?

[ilyes319]

yes that's a good place

[davkovacs]

We were discussing the implementation of layer specific number of channels.

Would this be a good place to put it? Is this PR planned to be merged in the near future?

[ilyes319]

yes it is a good place for a fork to develop that