switch from default to custom bisection solver, default causes issues for initial linear problem for a

adapt to removal of FirstOrderFunctional, use LineSearchSolver, remove contact obstacle dofs from direction

remove first order functional, compute eigenvalue locally in coordinateRestriction instead of globally

new program_state and fixpointiterator with makeLinearSolver, FunctionalFactory, NonlinearSolver working as intended

robust implementation of eigenvalue computation, prevents complex eigenvalues due to round-off errors