[WIP] HelpdeskFramework

DO NOT MERGE UNTIL RELEASE!

Trac ticket: https://trac.vikingco.com/ticket/6187

TODO list:

- [x] Base Bootstrap structure
- [x] Base class: BackOfficeBase
- [x] Base class: BackOfficeObject
- [x] Base class: BackOfficeView
- [x] Login / logout
- [x] Permission checking
- [x] REST API for frontend
- [x] Search index
- [x] Search gui
- [x] Rendering of BackOfficeObject
- [x] Rendering of BackOfficeView