added position_properties'; renamed prop to proposition; added attribute, method;
added position_properties';
renamed prop to proposition;
added attribute, method;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle