Builds an internal representation, based on ERT's smspec_node, of the SUMMARY section of an input file, that can be used to determine what data from a simulation to output. In essence, this is a simple map from DeckKeyword to smspec_node that carries over the interesting data. Introduces two higher order functions (map and concat) to aid in this, thoroughly isolating each case. Depends on ert pull request #1013 https://github.com/Ensembles/ert/pull/1013