This commit also introduces a tempprary fix to an issue where fab is
displayed on wrong screen when switching between bottom tabs rapidly.

Implement collapsing TopTabs on Android

specify `navBarHideOnScroll: true` in your `TopTabsScreen`

TopTabParams are a subset of ScreenParams, moved the properties that
are shared by both classes to BaseScreenParams.
This change was needed to report screen changes properly in ViewPagerScreen