Move files with low I/O priority

[John Peterson]

Please use a lower I/O priority for moving files (Advanced -> Set Download Location) than for other disk activity (such as downloading and uploading) so that download and upload isn't affected by a file move (possibly with a disk overloaded 100% message) .

Thanks!

uT 3.1.3-27120

Windows 7 x64

Update: This issue has partially been address with the multi-threaded i/o code since 3.3.