Gitlocalize alternatives

[mtdvlpr]

I've been casually looking for Gitlocalize alternatives, because I have now experienced a number of shortcomings (see my open issues). I looked at Crowdin and Transifex.

Crowdin looks very promising for a number of reasons:

• You can translate both the master and the docs branch from the same project
• Duplicate strings between master and docs will only have to be translated once (all setting labels exist in both branches)
• You can hide words that are not supposed to be translated (the ref property in docs md files)

Although these features are very nice, both platforms come with a big con: a much more complex UI. While I am looking at the administrator UI, it could be that the translator UI is simpler, but I doubt it (just confirmed with a second account this it is indeed not any simpler). I don't think exposing our translators to such a complex UI is beneficial. @sircharlo, what do you think? Have you considered these platforms before? What were your reasons for going with Gitlocalize in the first place?

[mtdvlpr]

Continues in #995