packagegroup-qt5-toolchain-target: Don't require qtquickcontrols-qmlplugins

The qtquickcontrols-qmlplugins requirement has been move to a runtime
recommendation so we don't fail in case it is not available.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
qtbase: Remove examples.pro file from packages

The examples.pro file is useless as we don't deploy the
source code. Remove it from the packages.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
qtsystems: Remove examples.pro file from packages

The examples.pro file is useless as we don't deploy the
source code. Remove it from the packages.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>