Original version of pyCSH

This release is the original version by Jon Lopez and Ziga Casar, as published in the paper

"Ziga Casar, Jon López-Zorrilla, Hegoi Manzano, Eduardo Duque-Redondo, Aslam Kunhi Mohamed, Karen Scrivener, Paul Bowen. pyCSH: Automated atomic-level structure generation of bulk C-S-H and investigation of their intrinsic properties. Cement and Concrete Research 183 (2024). https://doi.org/10.1016/j.cemconres.2024.107593"