Returns the value corresponding to key in the preference file if it exists.

	// Simple Editor Script that lets you create / save quick notes
	// Between Unity Sessions.
	class QuickNotes extends EditorWindow {
		var note : String = "Notes:\n->\n->";
		@MenuItem("Examples/QuickNotes")
		static function Init() {
			var window  = GetWindow(QuickNotes);
			window.Show();
		}
		function OnGUI() {
			note = EditorGUILayout.TextArea(note,
					GUILayout.Width(position.width-5),
					GUILayout.Height(position.height - 30));
			EditorGUILayout.BeginHorizontal();
			if(GUILayout.Button("Reset"))
				note = "";
			if(GUILayout.Button("Clear Story",GUILayout.Width(72))) {
				note = "Notes:\n->\n->";
			}
			EditorGUILayout.EndHorizontal();
		}
		function OnFocus() {
			if(EditorPrefs.HasKey("QuickNotes"))
				note = EditorPrefs.GetString("QuickNotes");
		}
		function OnLostFocus() {
			EditorPrefs.SetString("QuickNotes",note);
		}
		function OnDestroy() {
			EditorPrefs.SetString("QuickNotes",note);
		}
	}