Refactor autocomplete

Rewrite of frontpage autocomplete to:
- increase readability
- avoid duplicate event binding, and move binding to parent element
- remove duplication of DOM code
- introduce an anchor element, so URLs are handled natively by the
  browser
- remove rendering artifacts during typing
- remove references to 'trie', as it's not really a trie anymore
Merge pull request #257 from stianjensen/refactor-search

Refactor autocomplete