bedapub/besca: Besca 2.4

Major changes includes: dependencies to rpy2 and R libraries Rwrappers functions auto-annot comparison reports is now generic and include a riverplot R called into the notebooks + installation procedures Bug / warning fixed: if bbknn batch call contains only one category, waring is set up #112 exporting of a unique labelling is possible #105 Additional improvements: default datasets is now Kotliarov for the different notebooks. Small function to convert undirected signatures dictionary to signed one to use combined_signature_score as a routine; Updating URLs for Granja datasets (new Zenodo upload). some code refactoring in particular in export functions