Use shared pointers to Backend classes

The schemarouter now uses shared pointers. This removes the need to copy
the class.

Following changes move the member variables inside the Backend class.

server/modules/routing/schemarouter/schemarouterinstance.hh

@@ -24,8 +24,7 @@
 
 using std::string;
 using std::set;
-using schemarouter::Config;
-using schemarouter::Stats;
+using namespace schemarouter;
 
 class SchemaRouterSession;