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;

added generated file;

merged