Merge branch 'quit-handling' of git://github.com/dirkhh/subsurface

Merge branch 'quit-handling' of git://github.com/dirkhh/subsurface

* 'quit-handling' of git://github.com/dirkhh/subsurface:
  Use the last (or only) filename on command line as default for saving
  Show the "save changes" dialog before the main window is destroyed
  Check for changes at regular 'quit' events as well
  Catch changes to the info of the current dive when quitting
  Tracking changes to tanks is trivial
  Simplistic first attempt to get changes saved when quitting subsurface