Core: add some properties and signals to the FlickrReply object, to be able to better follow its lifecycle

Signed-off-by: Christophe <chris.chapuis@gmail.com>
Authoring: show flickr current running Flickr actions

Signed-off-by: Christophe <chris.chapuis@gmail.com>
Browser: fix items selection for photosets and collections of photosets

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