(bug 48075) Localise $wgSiteName, $wgMetaNamespace for dvwiki

Doing just that; I'm also adding 'Wikipedia_talk' as an alias
to NS_PROJECT_TALK for backward compatibility purposes, in
case there are some links using this namespace.

Bug: 48075
Change-Id: Ia4cdeabf8117dbc5f6c50500ccb5a052647474c9