Android compatible UI
Add Better debugging
Fix bug in callback support

Was forgetting to cal the cal;backs when the downloading the files.
Increase development expiration time
Add progress notification to PhotoRow
Unify getFile()

The File object now relies on getFile() instead of direct access to
the instance var. Allows easier refactoring.
Add toString() on File

For better debugging messages.
Update README on progress()

The former information was incorrect.