Changes

Summary

1. publish current log file, e.g. for easy error detection;
2. more options;
3. allow cancellation of Sessions.deps/base_info via progress.stopped (progress.echo only happens for options like "verbose");
4. tuned;
5. tuned signature;
6. merged
7. added server command "session_build": similar to JEdit_Resources.session_build;
8. tuned signature;
9. tuned;
10. more flexible preferences: avoid hardwired file; tuned signature;
11. tuned;
12. more operations for typed JSON values;
13. clarified signature;
14. clarified signature;
15. tuned signature; tuned output;
16. explicit Server.Context with output channels (concurrent write); support for Logger and Progress;
17. allow "." in message name;
18. re-use existing in/out streams;
19. tuned signature -- more generic;
20. tuned imports;
21. tuned;
22. tuned signature;
23. clarified signature -- do not expose socket;