Summary
- fixed markup
- ignore isolated nodes by default;
- merged
- cycle check with informative error;
- tuned: each session has at most one defining entry;
- more operations;
- tuned signature;
- tuned signature;
- Divided Topology_Euclidean_Space in two, creating new theory Connected. Also deleted some duplicate / variant theorems
- Session HOL-Analysis: Moebius functions and the Riemann mapping theorem.