Autotest: Move the README file to the tests/auto folder

So it is more visible. Add some tips if user needs to run
the autotests.

Change-Id: I86739a06b1cd62a061aec20fb640f7c66cfc557c
Reviewed-by: Liang Qi <liang.qi@digia.com>
Make GroupBox size respect anchor margins and update Gallery

We now implicitly add the margins to GroupBox so that you
can easily add them to a layout.

This also gets rid of the silly Sidebar example and adds a much
more useful Layout tab for effective testing.

Change-Id: I6026c32b2a198062d9b11a67245df0529aa61f8a
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>