raw -> .zarr of Geotek data

[Epta13]

As we spoke, the conversion of Geotek data files, which are already white corrected, should be done in the preprocessing, just untick white correction.

This is the pixel spectum before conversion, an it looks OK:

Once this the conversion without white correction is done, the spectrum is manipulated:

Can we fix this?

[guiwitz]

The reason for this is that when no processing is made, the data are never scaled properly. In the standard case, the corrected values are converted to integers by multiplying the data with 2**12 and here that never happens. So floats are wrongly directly saved as integers.

I added now a generic option to save data as floats ("Save as floats tickbox"). This can be used for this specific case, but also in general if you prefer to save the actual data instead of the ones scaled as integers (the reason for saving as integers is that it takes much less space). This is available thanks to 6f4346f.