Various fixes to Elasticsearch configuration

- It's now possible to specify http auth paramters in the URL
- I've changed the default port to 443 to SSL connections and 80 for
  non-SSL connections. Previously, both were set to 9200.
Merge branch 'issue-786' of https://github.com/kaedroho/wagtail into kaedroho-issue-786
Release notes for #802
Merge branch 'kaedroho-issue-786' into stable/0.8.x