Fix highlight segmentation tests

Closes #2465

See merge request !288

Highlights need segmentation informations. Waiting for identity % to appear is
not enough has it is given by another request to IMGT. This could cause some
test issues when this latter request ended before the one for the highlights

Fixes #2465

Export SVG to PNG

Closes #3240

See merge request !287

This is thus more similar to the previous export method.

Functinal testing should be performed before releasing or deploying.

Fixes #3463

Fixes #3240

See #3240.

From http://bl.ocks.org/Rokotyan/0556f8facbaf344507cdc45dc3622177
See #3240.

This reverts commit ba086042.
Now that the test has been fixed we want it to be run again.

Feature a/refactor lazy

See merge request !286

Factor a code that what called 4 times.

Fix segmenter_page test

See merge request !282

segmenter.py: Remove `-i` useless option

Closes vdj#706 and #3430

See merge request !283

This reverts commit ba086042.
Now that the test has been fixed we want it to be run again.

Fixes #3430, vdj#706

Improve width of numerical bar plots

See merge request !278

Features 2700, 2905 - bar x positions as in grid

Closes #2905 and #2699

See merge request !275

Prepares next commit.

It is .axisX.value_mapping.

Feature s/3171 stats multi samples

See merge request !269

Steps in integer axes should be limited.
Revert 7c7e3f84, rename the function and call it at a more convenient place.

Feature c/2699 nicer numerical values

Closes #2699

See merge request !274

See #2420 and (not merged) 068295d4.