Trying to clean up the mess with $wgCanonicalNamespaceNames and $wgExtraNamespaces.

Trying to clean up the mess with $wgCanonicalNamespaceNames and $wgExtraNamespaces.

Now those two together define the set of namespaces used in the wiki.
$wgExtraNamespaces is for user configuration and overrides, while
$wgCanonicalNamespaceNames is for extension adding their own namespaces.
No code should access those two directly for reading. Instead they should use
MWNamespace::getCanonicalNamespaces.

Also fixed indentation with spaces to tabs in Language.php