Neos 9 compatibility

[JamesAlias]

TODO

• [ ] Doctrine migration does not execute successfully because of removed json_array type used in Migrations/Version20160524125855.php.

  • Should we change the breaking migration's code to use flow_json_array?
  • Why is (this migration)[https://github.com/neos/neos-development-collection/blob/9.0/Neos.Media/Migrations/Mysql/Version20150913173832.php] working, then?

• [x] Update TemplateMailer when it's ready for Neos 9

  • PR: https://github.com/sandstorm/TemplateMailer/pull/17