Let cleanupCaps.php clean up when $wgCapitalLinks is set to true

Let cleanupCaps.php clean up when $wgCapitalLinks is set to true

This enables wikis to go from having $wgCapitalLinks = false to
$wgCapitalLinks = true (default).

Also:
* Declare $namespace member variable
* Fix regression introduced in ac53e45035e where non-dry run page move
was always considered a failure.
* Use MWNamespace::isCapitalized() instead of $wgCapitalLinks

Change-Id: I49caf8c1b49df1519d40b50d4aa26ea721db065d