Set the constraints=False, when doing Monte-Carlo simulations for R2eff.
This is to speed-up the Monte-Carlo simulations by a factor X10, when estimating the error for R2eff.
task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.
Authored by: tlinnet 2014-08-27
Parent: [r25332]
Child: [r25334]
