MXS-2556 Make config::Configuration aware of its object

The name of the object (i.e. the section name from the configuration
file), is now stored in the configuration object for that object.

That way, more contextual and hence morfe user friendly errors and
warnings can be generated.

server/modules/routing/smartrouter/smartrouter.hh

@@ -32,7 +32,7 @@ public:
     class Config : public config::Configuration
     {
     public:
-        Config();
+        Config(const std::string& name);
 
         Config(const Config&) = delete;
         Config& operator=(const Config&) = delete;