App: insert UUID property to trace the source of copied object

A property _ObjectUUID will be added to an object before it is being to
copied, if the property does not exists. Anoter propert _SourceUUID
property will be added to any copied object, with value set to its
source objct's _ObjectUUID.

src/Base/Uuid.h

@@ -50,6 +50,9 @@ public:
     const std::string& getValue(void) const;
     static std::string createUuid(void);
 
+    bool operator==(const Uuid &other) const {return _uuid == other._uuid;}
+    bool operator<(const Uuid &other) const {return _uuid < other._uuid;}
+
 private:
     std::string _uuid;
 };