Summary
- merged
- template for $ISABELLE_HOME_USER/ROOTS;
- tuned;
- clarified signature: provide all_known information uniformly (it is subject to Sessions.T selection);
- reverted 6acb28e5ba41: permissiveness of 1e5ae735e026 should be sufficient;
- tuned;
- tolerate errors in session structure, although this may lead to confusion about theory imports later on;
- clarified errors;
- clarified signature; tuned ssh.prefix;
- tuned;