Have admin option for how many files you can queue/upload at once in gallery and downloads

Because the current limit of ten is way too low for my purposes, and I shouldn't have to edit javascript files in a text editor to try and change 'file_queue_limit' every single time there's an upgrade or if I have to change the amount.

On that note, there shouldn't be two values for what might as well be the same thing, we shouldn't have a different limit for the gallery compared to the downloads or attachments.