Command.State: accumulate markup reports uniformly; Document_Model.token_marker: select relevant information directly from Markup_Tree, without intermediate HighlightInfo; tuned;

Markup_Tree.select: misc simplification, proper restriction of parent in subtree;

added Text.Range.- convenience;

tuned signatures;

alternative constructor for Range singularities;

concentrate protocol message formats in Isar_Document;

Branches.overlapping: proper treatment of stop_range that overlaps with end; Markup_Tree.select: allow singularity in parent range specification;

further clarification/unification of Position.Range and Text.Range concerning singularities: start offset is always included;

parameterized type Markup_Tree.Node; Markup_Tree.select: allow arbitrary interpretations, not just filtering; renamed Text.Range.intersect to Text.Range.restrict -- emphasize that it is not directly related to contains/overlaps;

added toString methods;

misc tuning and simplification;

updated some isatest settings;