combine options for additional node placement

[olwijn]

There are currently 2 options for placement of additional nodes:
concave_hull (under data_source) - From the manual: "When true, the bounding boxes of the gridcells of the original reservoir model are used to check if the generated additional nodes are positioned within the reservoir volume."
place_nodes_in_volume_reservoir (directly under flownet) - From the manual: "When set to true the boundary of reservoir/layer volumes will be used as bounding volumes to place initial candidates instead of using the convex hull of well perforations. Currently requires an input reservoir simulation model."
The difference or interaction between the two options is not entirely clear from the manual. The description for the concave_hull option seems incorrect: it defines a volume based on well node locations only. Since both options affect the placement of additional nodes it seems logical to combine these into a single option, e.g. "placement_of_nodes" with valid values "concave_hull" and "reservoir_volume". From the config parser code it is not clear which option is used as default.