A few more tuneups of mediawiki_singlenode:

- $Remove definition of $wgScriptPath
  (we don't need this because it's set by the MW setup script.)

- Set $wgServer to '"//" . $_SERVER["SERVER_NAME"]'
  (Allows https as well as http for static content)

- Allow overriding of apache site so that other classes can
  derive from mediawiki_singlenode and add https.

Change-Id: I77b6a640a2da1eaf4b4b7baa28b571fb6a387c63