Add taxonomy

[mathieugagne]

With the ability to create classification and sections there won't be a need to create dummy pages. For instance, if I have products and each one goes under /products, I won't have to create a page for /products but instead I would add a taxon. Taxons need SEO terms but that's all. Much simpler.

Request to /products

• look if it matches a page
• if not, look if it matches a taxon
• if so, load a taxon page or category page with children as excerpt

This is also removing the confusion behind a page where the content text is empty because the logic is in the template. If we need to add customizable content to a taxon page, we could convert it to a page.