RAII for auto-closing file streams

Small fixes I didn't want to include in unrelated PRs.

There are a few left in `storage.cpp` but since it's a single function
in 600 lines of code, I didn't want to touch the mess. The others are
safe to remove, cucumber and test run on Finland gives 👍.

include/util/graph_loader.hpp

@@ -194,7 +194,6 @@ unsigned readHSGRFromStream(const boost::filesystem::path &hsgr_file,
         hsgr_input_stream.read(reinterpret_cast<char *>(&edge_list[0]),
                                number_of_edges * sizeof(EdgeT));
     }
-    hsgr_input_stream.close();
 
     return number_of_nodes;
 }