Implement upgraded adopters shortcode

Resolves #252 (closed)

Implements the new eclipsefdn_adopters widget from EFSA which was rewritten in ES6 and supports templating.

Removal of config feature

Also removes the adopters config feature which was set through partials/footer_js.html.

Reasoning - I didn't see a config which was different than the one set in this repo. Why not simply use default values in eclipsefdn_adopters.js on EFSA? And if something needs to be different then simply set it as a shortcode param like we do for every other shortcode. Better for consistency. It is also easier to track what is affecting what since we have less files to worry about.