Made Treemodel interactive + made ScenarioList changable without reloading

So this should fix Bug #2942 (Treeitem / Treemodel reload without model reset). I had to change the treemodel for it. The ScenarioListView should now be changable without loosing the collapsed state. The were some buggy behaviours while creating this, but i think i caught them all. Please have a look at it i might have missed something though.