Function qr_decompose

* Decompose matrix \f$A\f$ using [Gram-Schmidt *process](https://en.wikipedia.org/wiki/QR_decomposition). * * \f{eqnarray*}{ * \text{given that}\quad A &=& *\left[\mathbf{a}_1,\mathbf{a}_2,\ldots,\mathbf{a}_{N-1},\right]\\ * \text{where}\quad\mathbf{a}_i &=& *\left[a_{0i},a_{1i},a_{2i},\ldots,a_{(M-1)i}\right]^T\quad\ldots\mbox{(column *vectors)}\\ * \text{then}\quad\mathbf{u}_i &=& \math