Install: Fix language selection flow, i18n sync, and labels

[christianbeeznest]

No description provided.

[ywarnier]

I'm merging it but I still see 2 issues:

• when my browser is configured to support the following languages, in this order: fr, fr_FR, en_US, when I'm loading Step1 with no cookies yet, I see this:

Obviously, there is some mix-up between the preferred browser language and the available languages available in Chamilo. In any case, it shouldn't show `fr` in the select box...

• the Portuguese language (pt_BR) does not show in the drop-down list, despite it being in Step1.vue. I'm not sure why that would be.