* Added `trace.EndpointInfo.LastUpdated()` timestamp
* Refactored `endpoint.Endpoint` (split to struct `endopint` and interface `Endpoint`)
* Added `endpoint.Endpoint.Touch()` func for refresh endpoint info
* Added `conn.conn.onClose` slice for call optional funcs on close step
* Added removing `conn.Conn` from `conn.Pool` on `conn.Conn.Close()` call