Layouts: increase the default spacing on mobile platforms

Change-Id: I7aff0236a08465c05559bd8a2e8a60b556fbc4ba
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@theqtcompany.com>
Revert "qquickrangemodel: don't emit signals before component is completed"

This reverts commit 774f2aa14e8742d77bb92968b06fab4dc35d79b4 that
broke sliders (auto test for RangeModel included to prevent that
from happening again) in the Qt Quick Enterprise Controls gallery.
Some sliders with a hard-coded range [0..360] and value 240 ended
up having a value of 0 at Component.onCompleted.

Change-Id: Ib3024c51c0552ac06528ba47b08e1a33a5f48324
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
ToolBar: fix spacing between menu button & content

Change-Id: I0e46e77186a8572c63c3eed7a99f35b948b87de3
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>