Add scripts/lists: wrappers of scripts/setconf for cmdline-like lists ("arg1=val1 arg2=val2").

Initial implementation. Does not handle value-less arguments.
scripts/setconf: allow for multiple comment signs (#).
scripts/setconf: add possibility to relax assignment rules (parse "FOO" as "FOO=").

In relaxed mode (-l) assignments with empty values are generated also in
relaxed mode.
scripts/lists: properly support value-less entries (thanks to -l switch in {s,g}etconf).