Fixed size matrices

Matrices of sizes $2\times 2$, $2\times 3$, $2\times 4$, $3\times 3$, $3\times 4$ and $4\times 4$ are represented by specific structures in Gandalf. There is a large set of functions which is repeated across every size of matrix. There is also a set of functions specific to square matrices. In both cases we will choose a single size of matrix and describe the functions available for that size. The sizes we will use are $3\times 4$ matrices for the functions available to every size of matrix, and $3\times 3$ matrices for the functions specific to square matrices.