Initial version of core ch

This improves preprocessing times in favour of worse query performance.
Core size can be set over the --core parameater, default is the old
behaviour to fully contract the graph.

data_structures/binary_heap.hpp

@@ -189,6 +189,11 @@ class BinaryHeap
         return inserted_nodes[heap[1].index].node;
     }
 
+    Weight MinKey() const {
+      BOOST_ASSERT(heap.size() > 1);
+      return heap[1].weight;
+    }
+
     NodeID DeleteMin()
     {
         BOOST_ASSERT(heap.size() > 1);

data_structures/search_engine.hpp

@@ -33,6 +33,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "../routing_algorithms/many_to_many.hpp"
 #include "../routing_algorithms/map_matching.hpp"
 #include "../routing_algorithms/shortest_path.hpp"
+#include "../routing_algorithms/direct_shortest_path.hpp"
 
 #include <type_traits>
 
@@ -44,6 +45,7 @@ template <class DataFacadeT> class SearchEngine
 
   public:
     ShortestPathRouting<DataFacadeT> shortest_path;
+    DirectShortestPathRouting<DataFacadeT> direct_shortest_path;
     AlternativeRouting<DataFacadeT> alternative_path;
     ManyToManyRouting<DataFacadeT> distance_table;
     MapMatching<DataFacadeT> map_matching;
@@ -51,6 +53,7 @@ template <class DataFacadeT> class SearchEngine
     explicit SearchEngine(DataFacadeT *facade)
         : facade(facade),
           shortest_path(facade, engine_working_data),
+          direct_shortest_path(facade, engine_working_data),
           alternative_path(facade, engine_working_data),
           distance_table(facade, engine_working_data),
           map_matching(facade, engine_working_data)