Search filter api

Integration of the search suggesstions (filters and topi)c in the homepage and search pages.

The search filter parameters aren't called "topic" anymore only. The parameter name is defined by the name of the filter group, e.g. this is a valid URL: https://developer-local.allizom.org/en-US/search?q=html&topic=api&type=tools&skill=intermediate

I could provide a list of filter groups so you can extend this condition `if(sParameterName[0] in listOfFilterGroupSlugs) {` if you want.