Added Nunit libraries.

Defined Container, which will hold our game pieces, and some simple unit
tests to go with it.
Added a ContainerColumn to replace the Stack

Implemented a bunch of addpiece logic for the Container
a better name for the Add Piece operation
minor whitespace cleanup
is the entire container full?
Changed ConnectFour.GameApi to ConnectFour.Game

GameApi sent the wrong type of message, I think.
added win detection when placing new pieces
using uint turned out to be more hassle than it was worth
tests for the match, debugging the tie and win conditions
cleaning up documentation and such