In fact instead of having to repeat those definitions n times we should have some king of a database defining those once for all

now also store noise_savgol_energy to be able to dispaly it latter.

[gui] change operations for the SpectrumViewer: now "_plost_xxx" operations should always return a list of CurveOperation instead of a single one.

An other option could be to return energy when calling for normalized_energy because this last attribut is only defined by PymCa.