Fix file sync error in Fx23+ for empty attachment paths

And fix reporting of non-OS.File file sync errors
Fix file sync error on Windows
Fix file sync error in Gecko 23+ if local file path is too long
Tweak error message for OS.File errors during file sync
Disable OS.File for file syncs on Windows <Fx25

stat.lastModificationDate returns the last access date
instead of the modification date due to bug
https://bugzilla.mozilla.org/show_bug.cgi?id=899436
Add missing semicolon
Update version and styles
Fix switching in and out of connector mode

Broken by 9d3f55be5193763d4c6d2afc3ddecea0bf5a9f39
Check if callback exists before calling
Return a promise from Zotero.shutdown()
Disable spellchecking in notes until it can be supported for real

https://forums.zotero.org/discussion/19771/workaround-to-disable-spell-checker/

Right now you can't iteract with it (to add/ignore words) or change the
language (which is probably only English in Standalone) or disable it
(without going to about:config).
Revert "Disable spellchecking in notes until it can be supported for real"

This reverts commit b82876253c9c4c349642b9df29b8c3182de87834.

We can just leave this alone until we have a proper fix.
Update versions
Merge branch '4.0'

Conflicts:
	chrome/content/zotero/xpcom/db.js
	chrome/content/zotero/xpcom/zotero.js
	install.rdf
	update.rdf