Add function and Fixed some question

[cnangel]

• add new function sum, sum the number of objects that match the specified checks. This will return the number of objects counted by the search. If an error occurs during the sum, the sum may reflect a partial sum. The real sum will be higher than the returned value;
• modify interface using latest of po6;
• fixed memory leak of value_to_attributes in util.cc;
• better free for hyperdex_client_destroy_attrs
• add java and python interface

[cnangel]

some patch fixed again