[Fix] Language for header: split in 2 parts, fix npm script for language

There's an issue: currently index-header text gets duplicated above & below buttons (Tutorials, Events, ...) in the header, instead of having top part with description and bottom part with 'start off by installing core workshop & subscribing to newsletter'. 
This PR: 
+ selectors: adds separation for top/bottom part of header - needs further work to edit all the existing translations (but, right now everyone, who specified index-header content has text duplication on live site & with new selectors they will fallback to english version)
+ language bootstrapper script: adds inserting of the html into  (so that you'll get links to subscribe/workshoppers) inserted in parts to translate (cc @watson on this) - this 
Maybe, change these 2 to use eq(0) & eq(1)?