Fix for url bug in the qmlvideo examples.

In the FileBrowser paths where being prepended with file:///, since all
the paths already starts with a forward slash, navigating away from the
initial directory was therefore not possible.

To make the examples work on Android, QT += multimedia was added.

Change-Id: Iff96729d476c4292999b022bdd6d5770b6b011e7
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>