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 
@pjackson28 Where would you recommend the links link to? Right now what is available on WET is the documentation pages for each theme. The current situation is the same where the title of the theme links to the documentation for the theme: http://wet-boew.github.io/v4.0-ci/docs/ref/themesstyle-en.html