clarified isabelle_hg (again, see b9d59669904a);

clarified signature: explicit Remote_Build.count instead of duplicate entries (see also ee8c014526dc);

clarified signature: more operations and options concerning Isabelle hg;

performance tuning: cache graph;

tuned signature: fewer warnings in IntelliJ IDEA;

unused (see also 004b39bf06a5);

clarified signature and modules: more explicit Build_Log.History;

tuned: avoid recursion;

tuned;

avoid duplicate data;

output more data;

tuned whitespace;