Fix to issue nest#683.

- A second template argument to member function register_connection_model of the ModelManager has been added, which allows the user to specify the type of connector model.
- An overloaded function to register_connection_model has been added that uses the default connector model GenericConnectorModel.

nestkernel/model_manager.h

@@ -180,13 +180,23 @@ class ModelManager : public ManagerInterface
   void set_model_defaults( Name name, DictionaryDatum params );
 
   /**
-   * Register a synape with default Connector and without any common properties.
+   * Register a synape model with default Connector and without any common
+   * properties. Convenience function that used the default Connector model
+   * GenericConnectorModel.
    * @param name The name under which the ConnectorModel will be registered.
-   * @return an ID for the synapse prototype.
    */
   template < class ConnectionT >
   void register_connection_model( const std::string& name,
     bool requires_symmetric = false );
+
+  /**
+   * Register a synape model with a costom Connector model and without any
+   * common properties.
+   * @param name The name under which the ConnectorModel will be registered.
+   */
+  template < class ConnectionT, template<class> class ConnectorModelT >
+  void register_connection_model( const std::string& name,
+    bool requires_symmetric = false );
 
   template < class ConnectionT >
   void register_secondary_connection_model( const std::string& name,

nestkernel/model_manager_impl.h

@@ -83,18 +83,18 @@ ModelManager::register_preconf_node_model( const Name& name,
   return register_node_model_( model, private_model );
 }
 
-template < class ConnectionT >
+template < class ConnectionT, template<class> class ConnectorModelT >
 void
 ModelManager::register_connection_model( const std::string& name,
   bool requires_symmetric )
 {
-  ConnectorModel* cf = new GenericConnectorModel< ConnectionT >(
+  ConnectorModel* cf = new ConnectorModelT< ConnectionT >(
     name, /*is_primary=*/true, /*has_delay=*/true, requires_symmetric );
   register_connection_model_( cf );
 
   if ( not ends_with( name, "_hpc" ) )
   {
-    cf = new GenericConnectorModel< ConnectionLabel< ConnectionT > >(
+    cf = new ConnectorModelT< ConnectionLabel< ConnectionT > >(
       name + "_lbl",
       /*is_primary=*/true,
       /*has_delay=*/true,
@@ -103,6 +103,14 @@ ModelManager::register_connection_model( const std::string& name,
   }
 }
 
+template < class ConnectionT >
+void
+ModelManager::register_connection_model( const std::string& name,
+  bool requires_symmetric )
+{
+  register_connection_model< ConnectionT, GenericConnectorModel >( name, requires_symmetric );
+}
+
 /**
  * Register a synape with default Connector and without any common properties.
  */