Fixes #17015 - Adds Key pairs controller

Fixes #17503 - Only trigger PXELoader suggestion when needed

Previously every host instantiation triggered a PXELoader suggestion,
which led to up to 3 extra queries per host loaded. This changes so that
the suggestion is only applied when a host changes it's OS.

Fixes #17487 - support sessions for api calls

- authenticated api calls save user to session and set
flag api_authenticated_session
- sessions with such flag allow posting requests without CSRF token
- api sessions exipre the same way as UI sessions
- api sessions don't store any additional data to keep the requests...

Fixes #15779 - make background processing available

fixes #17300 - accept Nic::Bond#attached_devices string inputs

Fixes #16548 - Changing user own passwd require current passwd

fixes #16725 - add plugin extension point for smart proxies

Fixes #14277 - Added description field to users

fixes #16514 - redirect to login page if user is deleted

Fixes #4608 - Added description field to role