Refactor of many AppStruct modules:

- Moved AppStruct.Application.ThreadedApp to AppStruct.ThreadedApp
- Removed AppStruct.Appplication.SecurityContext
- Moved AppStruct.Date.parsedatetime to AppStruct.Helper.parsedatetime
- Moved AppStruct.Date.__init__ to AppStruct.Date.py
- Moved AppStruct.Data.JSON to AppStruct.JSON
- Moved AppStruct.Data.Validator to AppStruct.Validator
- Added __all__ to AppStruct.Security