(bug 53904) Point local sidebars to UploadWizard on Commons

This patch makes $wgUploadNavigationUrl on multiple wikis
point to [[Special:UploadWizard]] rather than to the old
Commons upload page at [[Special:Upload]], which is used
by $wmgAltUploadForm anyway.

Local languages are passed to the UW via ?uselang=xx for
ease of use, just as it's done right now.

Bug: 53904
Change-Id: I849db76a74c81306a520a1fd7efc0d174bb1273a