Rebasing to Sage 5.2

As there were some changes to Sage since version 5.0 that also affect my code, I rebased my code from Sage 5.0 to 5.2. That meant installing the latest version, cloning a new branch "lattices", and manually copying over the lattices files and re-doing respective changes to some global files. I retained the 5.0-compatible version as a separate branch, whereas the main branch on github is 5.2-targeted. Of course, it would have been much easier if all of Sage was managed through git, so I'm really looking forward to that happening.