[Core] Adds: Permissions Entity and Interfaces

(references gh-23, #5051)
[Jobs] Adds Permissions awareness to job entities and paginator / acl / views

(references gh-23, #5051)
[Auth] Adds group management.

* Formular with Elements (Ajax enabled)
* Entities (Embedded Document "Group")
* Controllers
* Menus
* ACL rules

(references gh-23, #5051)
[Auth] Final code revision.

* Adds some icons to icons.less and rebuilds css
* Adds some presentation tweaks
* Adds documentation

(references gh-23, #5051)
Merge branch 'feature/Auth-user_group_management' into develop