clarified session_sources (again, see also 9d0e6ea7aa68);

clarified signature: more explicit types;

tuned output;

clarified signature: more general operations;

clarified signature: more explicit types;

clarified signature: more explicit types (see also 90c552d28d36);

do write_session_sources early, to have information available in build job;

tuned signature, following Url.append_path;

do not bundle Isabelle/Naproche, while it keeps changing;

tuned signature;

tuned;

clarified signature: uniform master_dir instead of separate field;

more standard master_dir;

tuned signature, following Url.append_path;

merged

more robust, for the sake of very rare duplicate files: src/Doc/Prog_Prove/MyList.thy and $AFP/Case_Labeling/util.ML;

store session sources within build database: timing e.g. 150ms for HOL and < 50ms for common sessions; enforce rebuild of Isabelle/ML to update build databases;

tuned signature;

tuned;

tunes signature;

clarified signature;

tuned signature;

more systematic Sessions.illegal_theory, based on File_Format.theory_excluded;

tuned;

unused;

tuned;

clarified modules;

tuned: no need to map master_dir, which does not participate in comparison;

tuned signature;

tuned signature;