Erase user's cipher key when onRestart() performed
For added security, the user's cipher key (if any) will now be cleared out as the app is restarted on the device's screen...after the app had been earlier superseded on the display by a different application. Also, the re-worded status line message "Long-press Textbox to access help file." better indicates that app documentation is a list item in the context menu. This fix in level 1.5.