duration formatter, makes time in sec easy to read

duration formatter, makes time in sec easy to read

The Language::formatDuration() method introduced by this patch let us
easily render an amount of seconds for easier human reading.

 $ maintenance/eval.php
 > var_dump( $wgLang->formatDuration( 1000 );
 string(25) "16 minutes and 40 seconds"

Also ran rebuildLanguage.php on Siebrands request

Change-Id: If287fb10e897d3d2374cf6eeae3bc5be00cdfc01