Duplicate NeighborlistCalculator code

[andrew_peterson]

There is duplicate code in gaussian.py, zernike.py, and bispectrum.py for NeighborlistCalculator. This can be moved to descriptor/init.py. However, the corresponding lines below if __name__ == '__main__': will also need to be moved to descriptor/main.py.

[andrew_peterson]

Also, the calculate method of this class takes an argument "key", which is not used. Is there some reason for this?

[Alireza Khorshidi]

I am surprised the NeighborlistCalculator is back in the gaussian.py, zernike.py, and bispectrum.py. I made an issue for this (issue #31 here) and fixed this in the commit aac3519.

The input argument "key" also seems to be extra.

[andrew_peterson]

Looks like you un-did this in commit 9895bbc. I think you ran into the issue I mentioned about needing to move the main lines of code around too.

[andrew_peterson]

Also, I noticed the other calculators have the key keyword; I think this is there for compatibility...