Remove old code generator class.
Rename NewCodeGenerator class to CodeGenerator.
Convert all parser tests from old parser class to new parser class (and they all pass !).
Remove old parser class.
Move AbstractSyntaxTree class from parser.h/cpp to ast.h/cpp.
Rename NewParser class to Parser.
Refactore parser error functions from global scope to static methods in parser class.
Convert all lexer tests from old lexer class to new lexer class (and they all pass !).
Remove old Lexer class.
Rename NewLexer class to Lexer.
Refactor all test involving float comparison to use the Catch::Detail::Approx() utility.