Please use po for translations

I'm filing this separate from #315 (closed) since it's a different topic (and sorry for the lots of issues opened):

Please use po for translations. This avoids having to maintain a separate mapping table in resources.rs by hand for translatable strings based on locale (not input method) as e.g. the fixed keyboards (emoji, terminal) in the popover. When translators add languages it will work out of the box without having to modify code to get that language working.

Let me know if I can help but the

textdomain (GETTEXT_PACKAGE);
bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);

should already go a long way.

This also avoids things like !496 (merged)