Angiogenesis

[cainja]

Implementing angiogenesis by adding a PatchGrowthComponent.

Size: xxlarge. (sorry)

The growth component can be registered to a PatchComponentSitesGraph to add edges over the course of a simulation according to the VEGF lattice layer.

Order of operations:

1. Iterate through all the nodes in the PatchComponentSitesGraph to search for nodes that have an average VEGF in the neighborhood according to the span of the possible offset directions from the node.
2. The sprouting direction is determined from three possible options: DETERMINISTIC (max VEGF concentration in neighborhood, BIASED (weighted randomly according to the local gradients), RANDOM (random direction)
3. Temporary edges are tracked and maintained according to the current state of the graph (which can change over the course of the simulation). If edges become perfused on the temporary version of the graph with these edges, the edges are added to the actual graph.
4. The edges are then updated with hemodynamics according to the calculation strategy - DIVERT (new flow is diverted from the corresponding edge), and COMPENSATORY (new flow is added to the artery).
5. The radii of the current edges is updated according to the calculation strategy.
6. Current graph is resolved according to the new state.

Still to be added: some more tests for the Growth component step method.

[kristaphommatha]

This is a partial review, I'll come back and look through it more over the next couple of days