[8] Rework saving to use interface and enable testing

Remove automatic saving from model, feeds, feed providers, articles and collections

ToDo

Custom:

• Remove automatic saving from model, feeds, feed providers, articles and collections
• Add new Interface to correctly save every component

Defaults:

• Report Changes in UML
• Report Changes in Wireframes
• Write Tests for every new non-view class

Acceptance criteria

Custom:

• Saving behaves the same but without saving as soon as anything is created

Defaults:

• Naming Convention for Classes, Functions and Variables are met
• Comments are sufficient
• Tests for every new non-view class are created and used in testing

Effort:

8