Runge Kutta DAE solver

Differential algebraic systems can be solved with an adapted Runge Kutta method.

This is an adapted Runge Kutta method (theoretical background e.g. in Hairer, Lubich, Roche "The numerical solution of differential-algebraic systems by runge-kutta methods") to solve DAEs. Already implemented is the Radau II A method of stage 1, 2 and 3 but basically every Butcher tableau can be implemented (see code for details). A simple example (the mathematical pendulum) is provided to show the usage. The nonlinear system solver is the newton method, but it can also be exchanged.