2.1.0-31

• update to libtorrent master
• using SWIG 4.1.1
• improved java api layer
• lt:allow to change save path without any additional actions
• lt:allow to change save path without moving any files
• lt:peer_list fix, clear the m_candidate_cache when clear peer_list, and set
  m_num_seeds to 0
• lt:schedule DHT announces using milliseconds rather than seconds
• lt:fix issue with web seed connections when they close and re-open
• lt:removing an already removed torrent is a no-op