move second order code from matlab to c++ code

[FFroehlich]

one of the few remaining things that are currently only accessible in matlab, but not from c/c++.

[dweindl]

As soon as this is done, reenable checks for sensitivities in second-order models (testfunctions.cpp verifyReturnDataSensitivities)

[paulstapor]

As I'm browsing through these issues right now...
I am wondering every now and then how to best re-implement second order stuff (even if someone else should do it at some point...)
I'm not perfectly convinced that the old matlab-style-way of augmenting the ODE model is really what we want... Also when doing second order, many things from first order can be reused, I think.

Maybe there's a way of doing this with a minimal wrapping overhead and with really most things done in C++ directly...
Any ideas? Obviously not urgent, just wanted to discuss it... (I am waiting for the compiler right now anyway... :D )