Randomise the initial 2D state of the grid

[georgikoemdzhiev]

Currently, the initial "Alive" cells are hard-coded in Main.cs

    private void RandomiseGrid()
    {
        // TODO implement good random algorithm
        _grid.CellGrid[2, 5].IsAlive = true;
        _grid.CellGrid[2, 6].IsAlive = true;
        _grid.CellGrid[2, 7].IsAlive = true;
        _grid.CellGrid[3, 6].IsAlive = true;
        _grid.CellGrid[3, 7].IsAlive = true;
        _grid.CellGrid[3, 8].IsAlive = true;
        _grid.CellGrid[3, 9].IsAlive = true;
        _grid.CellGrid[3, 1].IsAlive = true;
        _grid.CellGrid[3, 2].IsAlive = true;
        _grid.CellGrid[3, 3].IsAlive = true;
    }

We can use an algoritghm to randomise the grid instead.