Doc: Fix paths and add missing project files for QML and Quick examples

This change fixes a number of 'example path does not exist' warnings
from qdoc, and adds .qmlproject files for pure qml examples so they'll
appear correctly in the example manifest files.

Change-Id: Id0a424c4826fb5d8ebe6c3309bf33b976ff8477c
Reviewed-by: Geir Vattekar <geir.vattekar@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>