IssueTracker

The current bottom tab navigation doesn't follow the latest material design 2 guidelines:
https://material.io/design/components/bottom-navigation.html#behavior
- scroll position should be maintained between tabs
- pressing the tab again should reset its' backstack and scroll
- pressing back should go back in the current tab's backstack and then exit the app (it should not switch between tabs)
- each tab should have it's own backstack

(I am not sure which parts of this are already implemented, but the scroll/backstack support isn't there)."