Modified systemtest test_bug_negative_intensities_cpmg, to prepare for testing number of R2eff points.
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 2014-08-29
Parent: [r25442]
Child: [r25444]
