sync.profile: Point dependencies to an empty string

This means that we are going to use the same branch name for the
dependencies as the branch of the repository under test.

If we are testing the 'stable' branch, all dependencies will point
to the 'stable' branch as well.

Change-Id: I0959eea83b620af805b2113422bae5ae306af120
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>
Doc: Add Qt Quick Dialogs to Qt Quick submodules list

And add a landing page for Qt Quick Dialogs.

Change-Id: I0c2611bf5cdbf9937b4fd94228915553d8b3bb77
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>