Added Lesson 2: Parsing using antlr4

Contains the examples:
  * CSV: Parsing comma separated files (.csv). Just the quote-scaping ("") is missing for the real CSV files.
  * JSON: Parsing JSON files as defined in www.json.org
  * Boolean: Parsing boolean expresion containing AND (&), OR (|), NOT (~) and expresions enclosed in parentesis. It can be used identifiers for symbolic expresions. Also this  example is splitted in Lexer and Parser.

NOTE: The boolean example will be improved in the next Lesson.