New FileCopy task, minor UI usability features and some bugfixes.

- New FileCopy task: Simple copy of a given file to a target (file or directory). Overwrite flag added for safety.
- Fixed bug in FileScriptReader when reading a script file that does not specify a script "description" element.
- UI usability: checks to clear the log window before a script run and to focus on new log items as they appear.
- Sample .rant file to show FileCopyTask (sample2.rant)