Dev commit

Initial draft version of class Worker. All member functions for this Worker
are implemented. All other functions to be implemented are commented out in
//TODO comments.

There's one major problem left, need to redesign Set_writtable, competition
exists when Worker 0 and Worker 1 simultaneously want to write sth to socket,
when Worker 0 tried to Dispatch card and Worker 1 tried to Bcast Prime Claim.
Will fix this in later version.
Merge
Merge works done by X1n in Master and Phye's work on Worker.