This change makes the top bar a information/decorational item, not
interactive anymore.
- The menu at the top-right is redundant, it is provided by the
left-hand-side drawer and visually present through the botom-centered
control button.
- The back button is already provided on Android by default, swiping
back in the UI also works, so this button provides a third method to
go back -- that's overkill.
Less is more. Less top bar means more screen estate for the meat.
Signed-off-by: Sebastian Kügler <sebas@kde.org>