* i2psnark: Implement basic partial-piece saves across connections
    * i2psnark: Implement keep-alive sending. This will keep non-i2psnark clients
      from dropping us for inactivity but also renders the 2-minute transmit-inactivity
      code in i2psnark ineffective. Will have to research why there is transmit but
      not receive inactivity code. With the current connection limit of 24 peers
      we aren't in any danger of keeping out new peers by keeping inactive ones.
    * i2psnark: Increase CHECK_PERIOD from 20 to 40 since nothing happens in 20 seconds
    * i2psnark: Fix dropped chunk handling
    * i2psnark: Web rate report cleanup