RFC: indicate visually that the top bar is draggable

[Thomas Pfeiffer]

> ok, lets close this request with the mentioning: we show this feature
> exclusively on the introduction video, so every user will sooner or
> later find out.

We need to make sure that this actually works, though. I once showed
my PA Wetab to a stranger on a train. He did watch the intro video,
although while talking to me. He did not get the draggable bar at all.
So we need to test-drive this with as many users as possible, answering
the question: "Do users who only watch the video recognize that the
bar is draggable afterwards?" If it works for the vast majority of users,
we're fine. I think making watching the intro video a requirement
for being able to use the system is okay since it's only a two minutes.
Besides, that's also what Apple did with the iPhone gestures, the only
difference being that they didn't need to put the introduction video
on the device because pretty much everybody who bought an iPhone
had already seen the commercials demonstrating the gestures (see also
http://www.sendung.de/2010-12-23/on-intuitiveness-and-the-iphone/ ).
If not, we need to either improve the video or add some sort of visual cue
to the bar.
Maybe the draggability is just introduced a little too late in the video.
I can understand that we wanted to introduce the core concepts of
Contour - using, switching and setting up Activities - first, but I think
these things are actually more obvious (at least the fact that you can
do _something_ with the activity switcher or the + button) than the
fact that the top bar is draggable.
On the other hand, I don't think there is no unobtrusive way to 
indicate the fact that the bar is draggable. Maybe we don't need
a big icon but just a small visual cue. Perhaps Nuno has an idea on
that?

Thomas