Tagged all those examples that work on an Android device

This change enables the developers to list all the tagged
examples on the Qt Creator welcome screen using the "android"
tag.

Task-number: QTBUG-30173
Change-Id: Ic09183eb441497506b2d35f0d83ecd5d73d724f5
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Christian Stromme <christian.stromme@digia.com>