Two interface to avoid duplicated code, IQLParser is implemented by the
parsers generated by ANTLR and returns the forms the expr and the stmts.
IQLParserWrapper is responsible for parsing setting up the parser etc.
QLParser implements the new IQLParser Interface.
QLParserWrapper replacing the ANTLRParserWrapper and the Parser
Affected code updated
Removal of old files and updating import in StmtTypeChecker
Grammar including the three new methods and parser and lexer updated
Cast tp builder pulled up to Wrapper
Updated parser in checked extension
Updated execution code and wrapper in check extension of ql
Fixed error: used the wrong wrapper