New auto save option - Save an unsaved project

This new option will prevent people like me - that sometimes forget to first save the project - lose all our hard work after a unrecoverable crash. This situation was reported many times in the forum.
A "temporary" file is saved at preferences folder and is named unsaved.wings. After the unsaved project be saved the file is removed.

NOTE: Added a new option to auto save an unsaved project. [Micheus]