Formal languages block

Formal languages block centralizes code for scanning and parsing of different languages. For now it is used by Preg and CorrectWriting question types, but other plugins can use it as well.
This is technical plugin, containing code for lexing (scanning) and parsing text on different languages. For now it can do scanning for english natural language and C and C++ programming language. It is used by Preg and CorrectWriting question types. Feel free to use it in you plugins when you need quality scanning and parsing.
Teachers can add this block instances to the course to manage which languages will be visible to question creators in that course.