Import formation information from each realization in a grid ensemble

[magnesj]

Investigate how to import and use formation information across realizations in a grid ensemble. This information is stored in LYR files, and contains references to a named collection of N k-layers. The number of k-layers can vary between realizations.

Investigate how the layer information can be used at the ensemble level. It would be useful to guide the well target cluster algorithm based on a named formation layer.