COMPLETE Switch Config-setings to JSON, separate config/ folder (recreated on startup) from Declaration/ one

* Store WorkingDir as relative to App's Path.
* Selected Editor done via System.Diagnostics.Process.Start and  editor.exe instead of Shell and Path for notepad.exe.
* Minor GUI-work (set icons to dialogs)

AMIDST Switch Config-setings to JSON, separate config/ folder (recreated on startup) from Declaration/ one

* cSettings: objectify IO of settings, use try/catch for its error handling.
* Use json-schema to check settings.
* Open editor for text-files with System.Diagnostics.Process.Start instead of Shell and use Path.
* Utility routines for formatting msgs, joining file-paths.
* Add reference to Json.net dll.