if mbsync -v is less than 1.4.0 use old format, else use new format

[arosl]

Replace the check of apt-get with a check that looks at the version number of mbsync and use the old format if the version number is less than 1.4.0

[arosl]

fixes #936

[LukeSmithxyz]

You checked for it being not equal to 1.4.0.

Also, sort -V is not posix compliant.

[medicalwei]

According to their releases: https://sourceforge.net/projects/isync/files/isync/

I think a simple string compare should work?