[NEW] Photo: Add license support
[CHG] Collection: flat structure is changed to a tree structure
(collection has sub-collections)
[CHG] Collection: ability to create new collections
[CHG] Collection: new method to find set by name in current and
sub-collections
[CHG] Collection: new method to find collection by name in
sub-collections
[CHG] Collection: new method to add a set to collection
[CHG] PhotoSet: primary photo ID support
[CHG] User: getCollection can or not fetch sets (for performance)