Previously on Windows, where we don't have /bin/mv, we were recursing
into the data directory and copying files individually, which is very
slow, so automatic migration was disabled. Instead, try moving
directories with OS.File.move() with the `noCopy` flag. Moving
directories is technically unsupported by OS.File, but probably only
because of the possibility of a cross-volume copy (which is only
implemented for some platforms), and using `noCopy` hopefully prevents
that. If someone does have their data directory or storage directory on
a different volume, the migration might be quite slow, but leaving a
data directory behind in the Firefox profile directory (where it can be
easily misplaced with a seemingly unrelated Firefox reset) is worse.
Look for other profiles, from both apps (Firefox and Standalone), that
point to the data directory being migrated and update prefs.js in those
profiles to point to the new location.
Also reorganize code into Zotero.Profile and Zotero.DataDirectory
namespaces
