Added realization of proxy support to client.
Added longpoll_delta blocking request.
Added async function for longpoll_delta. Added request for restore (sync, async and task).
Added case for ApiType.Notify in ExecuteAsync and ExecuteAsync<T>.
Changed ApiType for GetLongpollDeltaAsync.
Check for min/max value of timeout param moved to RequestHelper.cs
Merge pull request #130 from partyz0ne/master

Proxy, longpoll_delta and restore