implements output generation through a dedicated JSON container:

- JSON syntax is not scattered over several files, but one place
- Reduces code duplication
- breaking changes:
  - new property in json(p) formatted response: "found_alternative": True/False
  - returned filenames now response.js(on) or route.gpx
  - /hello plugin returns JSON now

Include/osrm/Reply.h

@@ -58,7 +58,7 @@ class Reply
     std::vector<Header> headers;
     std::vector<boost::asio::const_buffer> toBuffers();
     std::vector<boost::asio::const_buffer> HeaderstoBuffers();
-    std::vector<std::string> content;
+    std::vector<char> content;
     static Reply StockReply(status_type status);
     void setSize(const unsigned size);
     void SetUncompressedSize();