Changes

Summary

1. merged;
2. more NEWS;
3. delete Isabelle distribution archive after use;
4. documentation for "isabelle build_docker";
5. updated for release;
6. tuned bib;
7. more documentation on view.antiAlias, not just NEWS;
8. more NEWS;
9. avoid premature crash due to missing session parents/imports;
10. avoid accidental update of base session sources (following documentation in "system" manual);
11. avoid duplicate stderr output in isabelle build -v, e.g. "Timing ..." (amending a829207b32a3);
12. prefer subpixel antialiasing by default: rendering of text is usually much faster, notably on Linux (see also 093ab1a99eb6 and f610115ca3d0);
13. slightly more explicit error, without going into the graph of proof futures;
14. more robust re-use of $ISABELLE_TMP_PREFIX (amending c1597167563e);
15. prefer strict qualification (default for 'interpretation', see 461ee3e49ad3) as proposed by Pedro Sánchez Terraf;
16. tuned documentation, based on hints by Pedro Sánchez Terraf;
17. backed out changeset 7eadccd4392c: too confusing wrt. text overview panel;