setup.py: add minimum required qrcode version

refs #2124
gnupg: gracefully handle error conditions when no data exists
tell windows users that we can't automatically sync for them yet

refs #2127
mtp_is_mounted() will never return True on win32 for now

refs #2127
Use the word 'save' instead of 'write' in user facing messages

Most people know what save means, while 'write' is more devspeak.
win32: after writing the CS keystore, pop open explorer.exe

fixes #2127
win32: fix the icons' datadir detection in windows
win32: ignore gvfs path setting on windows

apparently geting non existing env vars causes crashes
win32: update the pyinstaller spec files

one is for onefile mode and the other for older mode