v5-09-57b-01

Modifications to initialize TF1 from string and TVectorD

To allow for forward and backward compatibility between root 5 and root
6, the sigma parametrization function is initialized now from a string
for the function definition and a TVectorD for the fit parameters.
As input, the parameters are expected to be provided in a root file,
e.g.
 TFile*         /tmp/TF1_SigmaPar.root
  KEY: TNamed   SigmaParametrization;1
sqrt(([0]**2)*x[0]+(([1]**2)*(x[5]*[5])*(x[0]/sqrt(1+x[1]**2))**[2])+x[5]*AliTPCPIDResponse::sigmadEdxPt(x[2],x[3],[3])**2+([4]*x[4])**2
+((x[6]*[6])**2)+(x[6]*(x[0]/sqrt(1+x[1]**2))*[7])**2)
  KEY: TVectorT<double> SigmaParametrizationParams;1
  KEY: TNamed   MultiplicityNormalization;1     10000