more accurate isabelle_id: parent directory is not necessarily at tip;

clarified message;

more uniform id;

allow to provide external ISABELLE_IDENTIFIER for repository clone -- potentially relevant for isatest and mira;
clarified spaces in file names -- ISABELLE_HOME is non-critical after abolishment of "make";

isabelle version -i;

clarified situation about unidentified repository versions -- in a distributed setting there is not "the" repository;

removed Ids;

Merged in license change from Isabelle2004

New tool for displaying version information.