Work and updates to facilitate translation of the site via WPML plugin

[MirandaEcho]

We may need to make changes to Largo or to this child theme to ensure that all text is translatable

[benlk]

• run Theme Check plugin against caribbean
• patch obvious problems in caribbean
• add theme translation infrastructure from Largo to caribbean
• address Largo translatability issues noted in Improve translatability WPBuddy/largo#1592

[benlk]

One question for the client:

• For which languages/regions will they be creating translations? Please select from the options at https://translate.wordpress.org/

We can use Spain-Spanish with es_ES for now, but if there's a different one, it would be good to know.

[benlk]

Note that Largo for Caribbean is already at 0.7-prerelease, so we can continue to work on Largo for Caribbean as necessary; it's just a matter of keeping track of what's changed in Largo since that last commit.

[benlk]

Since the current Largo submodule commit f50df16e9e06fb9402802e2f1ce76ce058d26d76, here's what's changed in Largo trunk: WPBuddy/largo@f50df16...13e1777

CIJN has no styles regarding header-social, so that bit of the upgrade is straightforward.