Preparation for flatpack support (#255)

- Updates to project and desktop metadata in preparation for flatpak packaging
- These updates are independent of flatpack
- This commit unmingles the actual flatpack packaging from #255

glabels/main.cpp

@@ -46,6 +46,7 @@ int main( int argc, char **argv )
 	QCoreApplication::setOrganizationDomain( glabels::model::Version::ORGANIZATION_DOMAIN );
 	QCoreApplication::setApplicationName( glabels::model::Version::APPLICATION_NAME );
 	QCoreApplication::setApplicationVersion( glabels::model::Version::LONG_STRING );
+	QApplication::setDesktopFileName( glabels::model::Version::DESKTOP_FILE_NAME );
 
 	QIcon::setThemeName( "glabels-flat" );