[misc] set Rufus next to v1.4.6
[loc] Add Bulgarian translation

* Closes #295
[loc] minor updates to Russian translation
[iso] fix unwanted 'Unsupported NM flag settings' messages

* Closes #297
[syslinux] fix vesamenu.c32 errors

* Closes #298
[net] fix an exception in DownloadFile()

* As per the MSDN, HttpOpenRequest's 6th parameter should be a NULL
  terminated list
[ui] improve checkboxes handling

* Closes #294
[ui] don't remove the checkboxes when formatting

* Previous patch was creating an issue when creating an XP bootable drive for instance
* Also use our IsChecked() macro rather than IsDlgButtonChecked()
[ui] ensure the default download directory for updates is the current app dir

* Closes #299
* Also fix update save dialog not retrieving the path when compiled for Vista or later
v1.4.6 (build 440)
[loc] update Lithuanian translation to v1.0.10