Exporting strings for 9.0 with Xcode 9

[Stefan Arentz]

For lack of a better place for documentation:

I tried to export strings with Xcode 9b5 but that resulted in an export
where strings were heavily moved between files. That will cause a lot of
trouble I think, invalidating a ton of unchanged strings.

https://github.com/mozilla-l10n/firefoxios-l10n/pull/29

To not have to deal with that, I exported the strings with Xcode 8.3.3
instead, which resulted in a clean export, pretty much as was expected.

https://github.com/mozilla-l10n/firefoxios-l10n/pull/31

Just some minor nits that I'd like to resolve before we finalize this.

S.