- Some source code refactoring
- The PTYPE can have ACTION to validate parameter. The PTYPE's method must be set to `method="code"`. ACTION must return 0 on success and any other value on error. You can get parameter's value to validate by name `value`. If you want to change value of parameter (make uppercase for example) you can output new value to stdout within ACTION.
- The PTYPE has `completion` field now. It will be used if PARAM's completion is not defined.
- The user can press "Enter" or "Space" for illegal commands and arguments. The error message will appear. Earlier engine doesn't allow to press such keys (pressing had no effect) for illegal command line.