Added AutoSave feature as an enhancement

This consists of a pop-up, which includes a "Remember this decision" check-box, that pops-up every time the user tries to run a sketch that hasn't been saved, and gives the user the option of saving and running the sketch, or running it directly without saving.

However, the AutoSave feature has deliberately been left out for an untitled sketch, since untitled sketches are often used for prototyping.
In the current implementation, I have set the modal boolean of the JDialog to true, which makes it a blocking JDialog and prevents anything further from happening until the user makes a choice (or closes the window).

So basically, it is `run -> dialog prompt -> user clicks a button -> only then, sketch starts running`.