[orangecontrib][larch] add a call to `_updateProcess` on larch widget initialization to insure `_larchSettings` is updated if there is no modification of the parameters

It would be better to associate each key with a "condition": mandatory, optionnal...

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.