new functionality for power law derivative fitting

-- including prior in derivative fitting
-- new log-likelihood calculation
(PowerLawFittingModel._derivProblem_logLikelihood)
-- new Jacobian and Hessian calculations
(PowerLawFittingModel._derivProblem_Jacobian and _derivProblem_Hessian)

Also: new choices for ordering of parameters (connectionOrder and
typeOrder)
update default params for powerLawYeastOscillator

other minor changes