Add new Getting Started page

Modified content in start-en.hbs to match the new theme, 
Added page specific css in content/_base,scss
Modified colours in main/_base.scss and footer/_base.scss
Modified link colours in _variables.scss 
Actually never mind, it is used elsewhere as well. I'll just create a linkage between "about" and "tmpl-about" in the CSV file so they can benefit from each other's translations.