simplify neutrino-image recipes
luaposix: factor out common stuff, add version 31

* add luaposix.inc which contains common stuff
* add recipe for luaposix version 31 which adds lots of useful stuff
xupnpd: improve neutrino plugin

* rename from "coolstream" to "neutrinomp", it depends on
  neutrino-MP features now
* use luaposix' socket(), connect(), read() to retrieve http
  from web-if instead of forking wget