CONFIG REWRITE: don't throw some options on config rewrite

Those options will be thrown without this patch:
  include, rename-command, min-slaves-to-write, min-slaves-max-lag,
appendfilename.
CONFIG REWRITE: no special handling or include and rename-command.

CONFIG REWRITE is now wiser and does not touch what it does not
understand inside redis.conf.
Clarify include directive behavior in example redis.conf.