Modernize the code base to C++11 standards and beyond.

Apply `clang-modernize` (based on Clang 3.6) transformations to the
codebase while making sure to support Clang>=3.4 and GCC>=4.8.

We apply the transformations in parallel to speed up the quite
time consuming process, and use our `clang-format` style file
to automatically format the code respecting our coding conventions.

We use the following self-explanatory transformations:

* AddOverride
* LoopConvert
* PassByValue
* ReplaceAutoPtr
* UseAuto
* UseNullptr

This required a `compile_commands.json` compilation database, e.g.

    ccmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_EXPORT_COMPILE_COMMANDS=1

for CMake or check Bear for a Makefile based solution (or even Ninja).

    git ls-files -x '*.cpp|*.h' | \
      xargs -I{} -P $(nproc) clang-modernize -p build -final-syntax-check -format -style=file -summary -for-compilers=clang-3.4,gcc-4.8 -include . -exclude third_party {}

Boom!

References:

* http://clang.llvm.org/extra/clang-modernize.html
* http://clang.llvm.org/extra/ModernizerUsage.html

plugins/match.hpp

@@ -73,7 +73,7 @@ template <class DataFacadeT> class MapMatchingPlugin : public BasePlugin
 
     virtual ~MapMatchingPlugin() {}
 
-    const std::string GetDescriptor() const final { return descriptor_string; }
+    const std::string GetDescriptor() const final override { return descriptor_string; }
 
     TraceClassification
     classify(const float trace_length, const float matched_length, const int removed_points) const
@@ -211,7 +211,7 @@ template <class DataFacadeT> class MapMatchingPlugin : public BasePlugin
     }
 
     int HandleRequest(const RouteParameters &route_parameters,
-                      osrm::json::Object &json_result) final
+                      osrm::json::Object &json_result) final override
     {
         // check number of parameters
         if (!check_all_coordinates(route_parameters.coordinates))