Added INTEGRATOR_Z0, INTEGRATOR_RX0, INTEGRATOR_ZF and INTEGRATOR_RZF to Integrator signature, #504
Fixed broken example, #504
Implemented new Integrator signature logic, #504
Removed z_, rz_ fields in IntegratorInternal, activated new implementation, #504
Removed init_z, init_xdot fields and options from IdasIntegrator, #504