VID-1985 Add caching to getVideoDetail. Increase caching VM

Just to add my $0.02 late in the game; Cent 1: you could probably add this function to `includes/wikia/GlobalFunctions.php` as something like `wfEnsureArray`.  This "make an array whether you've got a string or array" happens all over.  Cent 2: I'm always in favor of splitting out functionality, reused or not, if its named well the cumulative effect keeps the parent function from being a 100's of lines long.