Extracting network backbones

Create/offer similar functions in the future as the ones in '[NetBone](https://gitlab.liris.cnrs.fr/coregraphie/netbone)' to extract network backbones. Look into what other R packages such as '[backbone](https://github.com/zpneal/backbone)' and/or '[disparityfilter](https://cran.r-project.org/web/packages/disparityfilter/disparityfilter.pdf)' as well in this regard. 

