Full CRUD support

[BartWillems]

Currently, I implemented some functions at random. Every model should have Create, Read, Update & Delete support.

Status as of 15/11/2017:

Room:

• [x] Create
• [x] Read
• [x] Update
• [x] Delete

User:

• [x] Create
• [x] Read
• [ ] Update
• [ ] Delete