POAS abstract question

Abstract question type used in questions developed by POAS department of Volgograd State Technical University. Contains some generally useful question type code.
This question type is a hub, containing code used by several question types and other plugins, developed by POAS department of Volgograd State Technical University:
backup and restore support for extra_question_fields;
Unicode string class that allows correct using of [ ];
base hinting classes for questiontype-specific hints;
Moodle Forms class for a textarea witht an  icon button on the right;
PHP libraries for lexical analysis using PHP string as a file.
If you are a developer and interested in using this code in your questions or other plugins, please contact project contributors.