[RM-7077] STD estimation outside lines

Created on 2022-02-24 09:30:05 by Didier Vibert. % Done: 0

bug in computing the std outside lines n the function @CLineModelFitting::getOutsideLinesSTD@

this fuction is for detecting a difference between the actual noise in the spetrum and the given variance.
the std of the spectrum is computed as the mean of the squared diff of spectrum and continuum outside lines (the continuum beeing the scaled fitted template or median estimated, depending on the parameters).

whereas it should be the STD of the spectrum (outside lines), ie the mean of the squared diff of the spectrum and its mean value, on sliding windows outside lines.