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 
These are changes to the WET theme itself. The changes should be made directly in the theme CSS. Just make sure that you use classes to target the effect of your CSS changes to the appropriate scope.