Fix error when refreshing the GUI after renaming a neuron with shift+F2.
Merge branch 'master' of github.com:acardona/CATMAID
graph.py: add try/catch for computing synapse risk

For an unknown reason, rarely an edge fails.
Removed a number of print statements from python files.
connectivity weidget: do not list skeletons under synapse threshold
Merge remote-tracking branch 'upstream/master'