SVN_SILENT made messages (.desktop file)
[API change] use GeoDataLatLonBox instead of GeoDataLatLonAltBox
only emit projectionChanged() signal if projection really changes
add projectionChanged() notification
simplify MapViewWidget::setMapThemeId()

* make code more straight-formward: first update celestial body combobox, then map theme list (the latter depends on the former)
use QxtFlowView