WIP component add tesseract 4.0 and dependancys to slapos

This commit contain tesseract4.0 and its up do date leptonica dependancy as well as a python wrapper that use tesseract API to do text recognition.

Currently, the wrapper cannot initialise the api as intended and the traineddata emplacement is not set (an new environnement variable should be introduced in zope, but it should be possible to "force" a new path with a patch that change the tesserocr _DEFAULT_PATH value).