[Echo.API.Transports.WebSocket] update subscribe machinery to determine the event;
update view in case of reset subscription;
queue requests by subscription while subscribe/request is not subscribed;
checking if connection is opened before sending requests;
[Tests] add tests for the Echo.API.Transports.WebSocket;
[Tests] update StreamServer.API tests to work with new interface;
[Tests] add tests for the Echo.StreamServer.API in case of using WS (WIP)