Add option for selecting language

[retrue]

I am Spanish, my computer is in Spanish, but I use all my fractal software in English, even the few ones that have Spanish translations.
Could you add, please, a menu to select language, instead of authomatically selecting the default one?
Thanks.

[kovzol]

This should be possible as explained at https://stackoverflow.com/questions/15355156/is-it-possible-to-change-language-on-qt-at-runtime and https://wiki.qt.io/How_to_create_a_multi_language_application. It seems we need Qt 5.10 to use the simpler approach. (Ubuntu 18.04 uses Qt 5.9 and we want to support it, so we are stuck to 5.9.)

[kovzol]

c19ff3f resolves this, however, currently XaoS has to be restarted to set the new language. Maybe we can do it more cleverly for 4.1, and maybe we can use Qt 5.10+ for 4.1 if we want to drop support for Ubuntu 18.04. Actually Ubuntu 20.04 LTS will be out in two months. See also https://unix.stackexchange.com/questions/481063/ubuntu-18-04-1-lts-x64-how-to-update-qt-5-10-from-qt-5-9-5 and https://reposcope.com/package/qt5-default.