Resolve "Migrate code to OTB 8.x"

Closes #5

See merge request !6

Workaround
orfeotoolbox/otb!976

While the real bug fix shall happen in OTB, we can work around it by not
setting the ProjectionRef to an empty string.

and improve reporting of errors on metadata extraction

Resolve "Migrate code to OTB 8.x"

Closes #5

See merge request !4

and make it compatible with OTB7 and OTB 8

This musn't be reset everytime we enter an thread!!

WIP: because we still need to use geoid file even if $OTB_GEOID_FILE isn't set

Resolve "Add -mean option to ExtractNormalVector"

Closes #6

See merge request !5

Resolve "Automatically inject NODATA metadata in generated images"

Closes #4

See merge request !3

Merge branch '4-automatically-inject-nodata-metadata-in-generated-images' of gitlab.orfeo-toolbox.org:s1-tiling/normlim_sigma0 into 4-automatically-inject-nodata-metadata-in-generated-images

Resolve "Adapt DiapOTB SARCartesianMeanEstimation to keep shadows"

Closes #2

See merge request !1

Use a mean on valid all low, high, left and right points, instead of only one
point each time.

TODO: Add an option to let us choose: one psingle point or mean

The conversion to int16 will be done after orthorectofication

However the output mask receives a 2 instead of 0 (nodata), or 1 (nominally
computed)

by commenting out logs

And check most likelly invalid states first ({0,0,0} is more likelly to happen
than nan's)

Avoid float -> double -> float conversions: works on floats all the way down