prefer Isabelle options for CI mail settings over ci.properties;

Added the command nxsketch, which is like sketch except it separates these subgoals by "next" fills in the context using "fix"/"assume" rather than "for"/"if". Also the sketch command does the same if there is only one subgoal.

proper cut for Parse.enum1' and its derivatives (see also 769abc29bb8e);

unused (see fe9e590ae52f);