Make Process.AddStream "functional" for testing

Back-end call still missing !
Merge remote-tracking branch 'origin/Front'

Conflicts:
	EvernestFront/EvernestFront/Stream.cs
Fix return types following Answers deletion
All endpoints added
Add paragraph about data selection
Merge remote-tracking branch 'origin/master' into Front

Conflicts:
	EvernestFront/EvernestFront/Process.cs
	EvernestFront/EvernestFront/Stream.cs