Remove unused code
Transform thesaurus preset into doctrine Entity
Bump to version 3.9.0-alpha16
Merge pull request #1027 from romainneutron/setup-upgrader

[3.9] Remove unused code
Merge pull request #1017 from nlegoff/edit-preset-entity

[Ready][3.9] Transform thesaurus preset into doctrine Entity
Convert custom events to symfony events
Bump to versio 3.9.0-alpha.17