libdmn: new anysin-to-string funcs + refac
simplify unique desc for monitored addr
Bugfix: simplefo w/ defaulted monitoring now works

Apparently simplefo combined with default http monitoring
  (as in, no service_types specified at all) has been broken
  for years - I guess nobody reported it because nobody
  really uses simplefo much at all, much less with default mon.
Merge branch 'master' into 2.x
get rid of "default" http monitor + "none" alias

The new default is "up", the only virtual service types are
  the forced states "up" and "down", and plugin_http_status
  is no longer pointlessly loaded for those that don't use it.
flip desc around for better sorting, eventually