Instantiate sparse data mat directly as transposed

[schalkdaniel]

The data matrix for spline data is created as n x p matrix at the moment. But it is stored as transposed to make use of column-major-order. Instead of transposing it, it would be much more efficient to directly create it as p x n matrix ...

[schalkdaniel]

Not 100% sure, but I guess its just flipping the location rows in the constructor of the sparse matrix ...