Contracting an edge joins two vertices into one. Their weight is added up, and the lists of edges is merged. For a common neighbor the edge weights are added up.

…tegration/implementation of wells.

Note: Code debt: Zoltan-specific types are overwritten/hard-coded. Also wrappers have the type of grid hard-coded to CpGrid.

Each well is a set of IDs of its vertices. The graph contains only one ID (the smallest), but functions will now check wells if the sought ID is not in the graph itself.
Wells are assumed disjoint, adding new well checks for intersections and possibly merges wells together. The check for intersections can be switched off to improve performance.

…ing remaining well cells

…lls is used

…d them

Asking for ID not present in the graph or wells will now throw exception.