Revert "Fixed minor bug in analysis.pourbaix.maker"

This reverts commit f0e814c69442cee6cd3ac416e7e96f622bc7038f.
Revert "Pourbaix diagram framework, and ion type for storing ions.", to create new branch for Pourbaix

This reverts commit 82e0a854010a9b8ad44c642900445934ad8bcfc1.