allow keyword tags to be redefined, but not the command category;

further amendment of "updated" edge (cf. 6ed49c52d463) -- required for repainting of unassigned command, e.g. for inactive buffe;

clarified command span classification: strict Command.is_command, permissive Command.name;

more robust bash interpolation;

more ambitious scalac options for makedist;

less noisy Isabelle/Scala build process;