Add a link Handlebars block helper and a load hook.

- Link Helper Usage:
  {{link route="post" params=optionalObject query="q=search" hash="anchor"}}
    Some Link Text
  {{/link}}

- Add a non reactive load hook for RouteControllers. The load hook is run by the
  router after the RouteController has been constructed but before it is run.
  This means before the "before" hooks, "action" function and "after" hooks are
  run. The load hooks are run in a nonreactive callback unlike before, after and
  action functions.