Improve maintainability of Case Studies styling

- Add quote and lead shortcode
- Add case study metadata in front matter (to generate page)
- Allow case study page to inherit similar styles from a centralised CSS file.

layouts/partials/css.html

@@ -27,6 +27,10 @@
   <link rel="stylesheet" href="{{ "css/training.css" | relURL }}">
 {{- end }}
 
+{{- if .Params.new_case_study_styles }}
+  <link rel="stylesheet" href="{{ "css/new-case-studies.css" | relURL }}">
+{{- end}}
+
 {{- with .Params.css }}
   {{- $extraCss := split . "," }}
   {{- range $extraCss }}