Update SASS/CSS and Grunt to align with the D8 version of Basic

Motivation:
I adopted Basic as my goto Theming framework when I moved all new Drupal development to D8. Consequently, I know the D8 version of Basic quite well but I'm lost in the D7 and have a couple of D7 re-theming projects to complete.

Solution:
I've updated a local copy of Basic 7.x-4.x so that it has the same SASS/CSS directory and file structure as the current Drupal 8 version and that doesn't rely on Ruby Sass and instead uses the SASS/Bourbon methods of the D8 version.

I'll upload a patch shortly with all of the changes.

Note: When installing the node_modules you run npm install from the root of the theme directory as you would with Basic 8