Fix signals to be saved

[frinio]

Audio signals that are being saved (i.e inverse, equalized), have a variable dB difference with the audio signals reproduced outside the app with the same coefficients.
This is caused by the normalization on the magnitude inside the app for the purpose of better visualization.

Update
If no normalization takes place, then the audio signals to be saved will possibly be clipped.
Leave this issue open, until I give it some more thought.

[frinio]

Pole fitting method does not normalize the inverse impulse response. It is passed as is to the main gui.

Check what is happening with the normalization throughout the app.

[frinio]

Make sure all calculations are done with the original signals and normalizations are applied in the end or when visualizations are enabled.

[frinio]

Functions to fix:
calc_correction_pushbutton_Callback and all functions that return the corrected_imp.