please exit with error code if something goes wrong

[GitMensch]

There is currently no non-gui option to see if something went wrong. To allow vdesk to be more useful for scripts setting the error code would be very useful.

> rem expected error code 9009 / 9059 (which is what `sdfdsfsdf` / `start sdfdsfsdf` would return or at least non-zero)

> vdesk run:sdfdsfsdf

> echo %errorlevel%
0
> rem expected error code 1 (to specify an error or at least non-zero)

> vdesk sdfdsfsdf

> echo %errorlevel%
0