Jacobian-Free-Newton-Krylov solvers and time integration methods

Solving equations of the form F(u) = 0 (Ariadne.jl) and u'(t) = f(t, u(t)) (the sub-package Theseus.jl developed in libs/Theseus).

Right now, please consider using NonlinearSolve.jl or the OrdinaryDiffEq.jl ecosystem. This package is in development.