separate FAB management in a helper class

CoordinatorLayout + FAB with "hide bottom view on scroll" behaviour
might seem to work, but there is a corner case when the view is just
large enough so that the FAB overlaps it, but not large enough to cause
scrolling and in this case it is possible to either be stuck with the
FAB over the bottom of the business area, or to hide the FAB without an
intuitive to make it pop up again

also, use single FAB for the Templates activity