Flickr API: fix UTF-8 handling in API usage

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Properties: show the Id of the current item

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
App initialization: fix a bug when retrieved collection is empty

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Authoring: possibility to remove a collection and a photoset

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Authoring of Photoset collections:
 - Possibility to create a new collection containing the selected photosets
 - Possibility to create a whole collection tree based on the entire photoset collection. Warning: this feature makes assumptions on the wanted collection tree based on the photosets names ([year-month ]path/to/node). A max depth of 2 sublevels is hardcoded.

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Collection selection: implementation of shift modifier, and fixes for control and simple (de)selection.

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>