Feature: Use Hooks for Jobs and Targets

[moreamazingnick]

Is your feature request related to a problem? Please describe.

What if jobs and targets are designed similar to the reporting module?

With primary key and foreign ids and a hook information and the "data" stored in a json text.
With that a custom module can for example provide functionality to fetch certificates/clientcertificates from any custom source. (git/folder/file/database/director-textfield)

Of cource this should be implemented after /in combination of #41 since import tasks should't interfear with the default truststore.

Since truststores could provide permissions there would also be the possibility to restrict access to the truststores.

Best Regards
Nicolas