The tab icon names are currently hard coded in the templates.
This commit lets us introduce an icon property in the future, e.g:
categories_as_tabs:
general:
icon: search-outline
Previously all categories were displayed as search engine tabs.
This commit changes that so that only the categories listed under
categories_as_tabs in settings.yml are displayed.
This lets us introduce more categories without cluttering up the UI.
Categories not displayed as tabs can still be searched with !bangs.
Markus Heiser
Alexandre Flament
Martin Fischer