removed experimental history panel;

more explicit modeling of Command and Command_State as Session.Entity; misc tuning;

updated;

tuned;

tuned caret_listener/selected_command;

misc tuning;

eliminated global Session.document_0 -- did not work due to hardwired id; more precise Session.begin_document, avoid race on var prover; replaced slightly odd Session.document_versions by Sassion.documents table (cf. src/Pure/Isar/isar_document.ML); simplified edit_document in ML: initial empty command is identified by ""; misc tuning;

tuned;

tuned;

Standard_System;