Moved Shotwell source to separate module
Renamed ImageSource._load_tags to .load_tags
Use mountpoint lstat result instead of database file one
Moved file backend specific image source code to separate class
Changed FileBasedImageSource._default_location() to property .default_location
Import sqlite3 in shotwell image source
Define command line arguments explicitly
Allow image sources to define command line arguments
Merge branch 'fixup-restructure'