Refactored IntegratorInternal::reset(B), #511
Added discrete time in RKBase, #511
Added taping to RKBase, #511
Added support for backward integration in RKIntegrator, #511
Refactored backward integration in RKIntegrator, #511
Refactored backward integration in RKIntegrator (2), #511
Bugfixed backward integration in RKIntegrator, #511
Refactored backward integration in RKIntegrator (3), #511
Refactored backward integration in RKIntegrator (4), #511
Added RKIntegrator to sensitivity analysis examples