Change rendering of pages

[TowardsDeath]

Currently:

• The controller renders any page as long as it's in the htmldev root dir.
• URL's end with .html.twig

How it should be:

• The controller should render the URL /htmldev/{section}, for instance /htmldev/components/cards
• In the components folder, there's a cards.html.twig that renders styleguide_component for each card defined in a card.yml.
• styleguide_component automatically renders the component along with the code required to render that component.
• Navigation is defined in a yml file.