Link creation at Nodes. Non-random link IDs.
Moved link deletion into Node
Obsoleting nodenet.links Part I
Unlinking now handled by Nodes
Reducing usage of nodenet.links
Removing get_link, which nobody but the tests ever
called
Removing the central link dict
Merge pull request #53 from joschabach/facade_links

Facade Links
be defensive against jumping to nodes outside viewport
Merge remote-tracking branch 'joscha/master' into feature_loco_graph