batch mode: Skip all uid < 1000 programs instead of only uid = 0

batch mode: Skip all uid < 1000 programs instead of only uid = 0

This fixes bug #63, but might have unexpected side effects. From a
comment in the commit:

> The following line assumes that user accounts start at 1000 and that
> no one works using the root or another system account. This is rather
> restrictive, but de facto default.  Alternatives would be to use the
> UID_MIN from /etc/login.defs or FIRST_UID from /etc/adduser.conf; but
> effectively, both values aren't binding in any way.  If this breaks
> your use case, please file a bug on Github.