Merge pull request #4 from felixmo/master

Fixes to credential input and implemented the ability to stop the upload operation
Make 'debug mode' switch work

Switching off debug mode lets you upload straight to Commons for real.
Also, debug mode now uses test.wikipedia.org.
Consolidated API initialization into [app startApi].
Fuller description format, include some categories.
Credentials are re-validated if debug mode option has been changed and an UIAlertView is displayed if credentials are incorrect.