Missing interceptors OpenConnector, Connect, ConnClose

[dolmen]

The interceptor lack callbacks for:

• Driver.OpenConnector(name string) (driver.Connector, error)
• Connector.Connect(context.Context) (driver.Conn, error)
• Conn.Close() error

I propose to add the following callbacks:

• OpenConnector(connector driver.DriverContext, name string) (driver.Connector, error)
• Connect(ctx context.Context, connector driver.Connector, name string) (driver.Conn, error)
• ConnClose(conn driver.Conn) error

Use case: tracking connection leaks (missing call to conn.Close)

[inconshreveable]

thanks for finding these holes in the interceptor. i'd be happy to take a PR for this!