[gui/util.h] add PRODUCT_NAME and PRODUCT_VERSION NSString* macros
[gui] Error handling!  Yay!!!!1!one!!1!

* There are two new log files in <config-dir>/logs:
    * AppBackupGUI.log (the GUI's stdout and stderr)
    * FixPermissions.log (FixPermissions's stderr only)

* If an error occurs on the Python side, the GUI will tell the user,
  give them the option of emailing the error to me (the two new log
  files are added to the email), and allow the user to continue if
  possible.  If the error is fatal, then the user will not have an
  option to close the error message, except by pressing the home
  button to exit the app.  (We don't run in the background.)  The
  top of the email is left blank for the user to provide a description
  of what they were doing when the error happened.

* Objective-C errors still un-gracefully crash, but they do appear on
  the GUI process's stderr, and the user can manually email the logs
  to me with a description of what they were doing when the error
  happened.

No dead parrots were harmed in the making of this changeset.  (And
neither were any resting ones.)