Possibility to work on multiple operations (rename, change category, change account)

New database version (2) :
		fix_cost for categories
		virtual account

src/model/User.h

@@ -37,6 +37,7 @@ class User
 public:
     User(Database* db);
     ~User();
+    void InvalidateOperations();
 
     wxString _id;
     wxString _name;