shad/MT: add thread safe unordered_set.
shad/MT: move srcs to folder src. change Makefile.
shad/MT: move messages code to separate file.
shad/MT: rename TThreadProcess -> TThreadWorker.
shad/MT: move worker to proper header worker.h
shad/MT: use TWorkerEnvironment object instead of queue holder.
shad/MT: add human consturctor for TTaskMessage.
shad/MT: add human wrapper StartWorker.
shad/MT: add message handlers.
shad/MT: move realization to worker.cpp, change Makefile
shad/MT: minor changes.