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 
It doesn't change what the CSS affects, it's the SCSS coding convention that we are using (always nest). So change it to:
```scss
.panel-body {
	h4 {
```