Changes

Summary

1. clarified signature;
2. clarified: follow "isabelle version -t";
3. further clarification of Isabelle distribution identification -- avoid odd patching of sources;
4. tuned signature -- more explicit types;
5. more robust and uniform ISABELLE_TAGS;
6. clarified ISABELLE_ID: distribution vs. hg archive vs. hg repos;
7. simplified release status (again), in contrast to a43898f76ae9;
8. more uniform HTTP resources;
9. clarified (again): local tip could be actually more recent;
10. tuned;
11. tuned;
12. clarified name;
13. more systematic java_library: avoid empty entries, declaration order as for other bash functions;