Semi-automatic check of alibuild recipes validity

Until we figure out, how to properly align with alibuild we need a script that will compare current state of external recipes with upstream with possibility to replace the improved recipes. In the beginning it is proposed to simply download external recipes, compare it with our current state and if there are differences, new version of recipes will be left available to the user to decide whether he wants to add them (manually) or not. No automatic replacement of recipes will be available for now.