Changes

Summary

1. tuned signature;
2. clarified signature;
3. tuned -- more robust against changes;
4. more robust: avoid race-condition of terminated vs. consolidated;
5. do not expose obscure flags;
6. clarified quasi_consolidated state: ensure that exports are present for ok nodes;
7. clarified Thy_Resources.Session.use_theories: "terminated" node status is sufficient;
8. tuned documentation;
9. more detailed node_status;
10. clarified bracketing of messages: [forked [running finished] joined];
11. NEWS;
12. clarified reset_notepad;
13. more robust reset_state: begin/end structure takes precedence over goal/proof structure;
14. no reset_proof for notepad: begin/end structure takes precedence over goal/proof structure;
15. clarified signature;
16. tuned;