added placeholder "validate" method to Property
added placeholder "validate" method to Property

bleib1dj/neomodel,wcooley/neomodel,cristigociu/neomodel_dh,robinedwards/neomodel,andrefsp/neomodel,bleib1dj/neomodel,robinedwards/neomodel,pombredanne/neomodel,fpieper/neomodel