Common lib: use integer parser and integer to string conversion to implement SeverLoction::From/ToString() methods, instead of ostringstream and istringstream in order to avoid stream objects construction and memory allocation overhead.
Chunk server: add missing using istringstream.
Chunk server: make remote sync state machine generic by moving RPC specific handing logic into the RPCs object methods where it belongs. Replace ostringstream and istrinstream in the frequently used RPCs request and response handling logic to minimize stream objects construction and allocation overhead.