returned scattering pattern xarray is not copied

[pdudenas]

The returned scattering pattern xarray is returned via reference(?), instead of a copy being made. This is an issue because if you do pattern1 = morph.run(), make some modifications to the morphology, and run pattern2 = morph.run(), pattern1 and pattern2 point to the same place in memory and pattern1 will be overwritten. For now this can be avoided with pattern = morph.run().copy()