Updating strings for localization [ci skip]

These strings have been uploaded to crowdin and ready to be translated.

localization/gen_translation_source.sh

 #!/bin/bash
 # This is set to find lupdate in my particular installation. You will need to set the path
 # where you have Qt installed.
-QT_PATH=~/Applications/Qt/5.7/clang_64/bin
+QT_PATH=~/Applications/Qt/5.9.1/clang_64/bin
 $QT_PATH/lupdate ../src -ts qgc.ts