refactor: update content structure and layout templates

- Updated author format in content files
- Added section field to content files
- Simplified categories format
- Removed no-category.html layout
- Updated list.html and single.html layouts
- Updated index.html layout
- Updated generate-content.js script
- Do not index content with git

content/informatique/2018-07-marktex-editeur-markdown-libre-et-gratuit/index.md

@@ -6,9 +6,10 @@ slug: "marktex-editeur-markdown-libre-et-gratuit"
 wordpress_id: 306
 excerpt: "Marktex un logiciel remarquable pour écrire du texte en Markdown. J’utilise souvent Markdown pour écrire mes articles. Le…\n"
 featured_image: ""
-author: {"id":1,"name":"Kevin"}
-categories: [{"id":14,"name":"Informatique","slug":"informatique"}]
+author: "Kevin"
+categories: ["Informatique"]
 tags: []
+section: "informatique"
 ---
 
 <p><!--kg-card-begin: html--></p>