Runs through all layer nodes, attempting to find layer nodes that are implemented by the specified class, then sets up a linked instance of the class for each. Allocates one linked instance to run each of the groups specified in the class, so state is shared. If a layer is not grouped (ie. NAME_None), then state is not shared and a separate linked instance is allocated for each layer node. If InClass is null, then all layers are reset to their defaults.