Added an edge_index parameter. Data is no longer copied, instead symlinks are used.
Experiment using an integer for identifying each entering edge
Merge branch 'develop' into feature/simpler-input-handling1
Now passes the tc_60_graph test
Added link_data_for_edge that creates symlinks
tc_50_node passes ok
Runner now creates links
subgraph execute is now working with links
removed dead code
Merge branch 'feature/simpler-input-handling1' into develop