[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

[FEATURE] Introduce the path_segment field that allows to give proper URLs yourself, Also a lot of cleanup was done

This commit solves a problem with jobs that do not have a department
set

This commit adds a new field and a new record type, the department.
It comes as a replacement for the area text field and allows for
department records to be created. This also introduces a migration
wizard, that can create new departments out of the old area entries.

[TASK] Using contact for email addreess, ts setting for default contact. General issues with the models

Also made sure you can apply for positions which aren't listed