Fix manylinux / pip issues

Fix #174 and #174

Pygtftk now depends on Python 3.9

Fix bug in README that prevent producing pypi packages...

Force pillow version between 7.0.0 and 8.3.2

Fix issue with new Pillow requirements and Pandas deprecation messages.

Documentation improvement. Fix a backward compatibility issue in pypa…

…rsing.

Contains several improvement in OLOGRAM.

Fix issue with Docker/Manylinux

Fix issue with manylinux