Removes Support for sg_seo < 5.0

[FEATURE] Allow more than one company assignment, Fix broken mail sending of unsolicited applications

[FEATURE] Add link to allow external job application URLs, some cleanup, TCA restructured a little bit

https://trello.com/c/3ocgBvPZ/3021-websitebase-alle-erweiterungen-pr%C3%BCfen-und-anpassen-des-tca-f%C3%BCr-syslanguageuid-und-auto-code-format-der-ide-in-den-tca-dateien

The title of the pop-up button was broken due to a typo.
Also, it was possible to set non-page links for the privacy policy page.
These options are disabled now.