Add ability to control the order in which mass import adds files from a local directory.

Replaces #126612: Acidfree mass import mis-ordered on certain filesystems

Depending on the file system, mass import may or may not add new files in any controlled manner, which can be frustrating if you want your images sorted chronologically. We should have an option to control the order the images are added - by creation time, alphabetically, etcetera.