Rename the QML function "centerOnCoordinates" to "centerOnCoordinate"
and pass a QGeoCoordinate to it in ::centerOnDiveSite().
This will prevent the creation of a QGeoCoordinate object on the
QML side and instead it will be created in C++.
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>