For multiple spectra analysis export matrix

Be able to export a matrix:

Add a button in the multiple spectra analysis that allows to export a matrix

There should be a dialog box with:
* from / to
* nbPoints
We will after reduce the number of points and export a matrix.

@hamed-musallam Please could you prepare this button and currently export an 'empty' file.

Please add in this ticket the place I should add the code. I should have all the spectra in the input of the function and I will create a method that convert the spectra to a text file.