start refactoring tirpan to fix remaining problems
improve unit tests
support "std01.py" test case on branch
support "std02.py" test case on branch
suport "assign0[23]" test cases on branch
support "std03.py" test case on branch
support "std05.py" test case on branch
support "func06.py" test case on branch
support "func09.py" test case on branch
support "builtin03.py" test case on branch
support "func10.py" test case on branch
support "func21.py" test case on branch
support "func1[1348].py" test cases on branch
support "func15.py" test case on branch
support "func16.py" test case on branch
support "func20.py" test case on branch
support "builtin01.py" test case on branch
support "std06.py" test case on branch
support "builtin0[26].py" test cases on branch
support "object01.py" test case on branch