Various changes: BioSystem, LIMEX_A, ODESolver,...

   Introduced a sysTol variable for setting maxCond individually.

   Got Hermite interpolation scheme up and runnnig.  Switching
   between Hermite and plain old LIMEX interpolation is possible now.

   Work towards enabling multiple integrators: got rid of BioSystemWrapper,
   replaced by the much more generic FirstOrderODESstem interface class.
   Introduced therefore two new classes BioSystem[ODE|VAR] derived from
   that interface as glue between ODESolver and BioSystem.

   The good news: there seems _no_ performance penalty for all these changes,
                  at least at first sight... keep fingers cross!