fill(value) {
                for (var i = 0; i < this.rows; i++) {
                    for (var j = 0; j < this.columns; j++) {
                        this.set(i, j, value);
                    }
                }
                return this;
            }
Fills the matrix with a given value. All elements will be set to this value.
@param {number} value - New value
@return {Matrix} this