Group Graph: export models with the name as shown in the nodes.
Merge branch 'master' of github.com:acardona/CATMAID
CircuitGraphPlot: use typed array for the adjacency matrix.

Speeds up computations a lot: now feels instantaenous.
GroupGraph: use typed arrays for the adjacency matrix, speeds up.

Additionally simplified populating the adjacency matrix, given that now
each graph node is a valid entry (be it a group or a fraction of a skeleton).