Rational HMC monomial for non-degenerate twisted mass doublet

This is an implementation of a RHMC monomial for the non-degenerate twisted mass doublet. Its not yet to pull in, but I opened this pull request rather for discussion. The new input monomial is

    BeginMonomial NDRAT
      Timescale = 1
      kappa = 0.170
      AcceptancePrecision =  1e-20
      ForcePrecision = 1e-12
      StildeMin = 0.013577
      StildeMax = 3.096935
      Name = ndrat
      DegreeOfRational = 12
      Cmin = 0
      Cmax = 11
      ComputeEVFreq = 1
      2KappaEpsBar = 0.0935
      2Kappamubar = 0.1105
    EndMonomial

`Cmin` and `Cmax` is the range of terms in the rational to be included in this monomial. This allows frequency splitting by distributing the same rational approxmiation over many timescales. `StildeMin` (`StildeMax`) is the minimal (maximal) eigenvalue of the squared even/odd preconditioned nd twisted Dirac operator. (see the documentation for details)

Heatbath and acceptance steps are checked and working. The derivative doesn't work yet, so any hint would be welcome...