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.

assets/scss/_case-studies.scss

@@ -2,6 +2,7 @@
 
 hr {
   background-color: #999999;
+  margin-top: 0;
 }
 
 h2 {
@@ -10,7 +11,7 @@ h2 {
 
 .subhead {
   padding-bottom: 2% !important;
-  padding-top: 0% !important;
+  padding-top: 0.75em !important;
 }
 
 .details {