Add help section listing groups & roles that can see me (Z-46, WIP)

[cdn64]

This proof of concept adds a section to the help page listing all groups & roles that can see the currently logged in user:

It adresses a feature request from PBS (cc @Michael-Schaer) and an older request in the forum:

hitobito sollte stärker kommunizieren, […] wer denn eigentlich auf meine Daten Zugriff hat. Es geht grundsätzlich ums Bedürfnis, ich will wissen, wer an meine Daten herankommt.

I'm unsure about the following aspects:

1. Whether the determination of «who can see me» is correct, and how to optimize this for multiple entries
2. Whether the placement of the section is good, or whether it should rather be put on a separate page
3. Whether this information is also wanted in hitobito core, and the implementation should therefore be moved

[Vento-Nuenenen]

I may suggest to add sections, who can see basic-infos (:show), see advances-infos (:show_details), see all (:show_full) and edit (:update).
Shouldn't be to complicated, but is a bit of an overkill...

[Vento-Nuenenen]

To keep better performance on your home-page it would be better to bring this on an separate page.
I think it could take a lot of time to grab all those infos on a person with many roles...