Represents a reference to an external wiki(Inter Wiki).
An InterWiki reference is a shorthand notation to reference a set of external URL, all having a common prefix (eg
http://server/some/common/prefix/a1, http://server/some/common/prefix/a2). An InterWiki reference is made of an
InterWiki Alias which is a name corresponding to the common URL and an InterWiki Path which is the suffix to append
to the common URL part to make the full URL.