adds dense vector class (vec)
adds sparse vector class (sparse_vec)
adds dense matrix class (mat)
adds sparse matrix class (sparse_mat)
adds general tools
adds gaussian elimination
adds jacobi, gauss-seidel, gradient
adds conjugate gradient (standard and Lanczos)
adds weighted jacobi
adds biconjugate gradient stabilized
adds max norm to sparse/dense matrices
fixes small bug on L^p norm of dense/sparse vectors
adds missing banner on jacobi class
adds missing generic iterative solver (for linear systems)
fixes small bugs on gradient solver
fixes small documentation typos
adds QR factorization with classical/modified Gram-Schmidt