1) Re-implemente 64-bit unique tracker id by composed of user configured id salt and current process pid.
2) Add UDP unicast livesync function with config livesync.cluster.batch_unicast,
   for details to see opentracker.conf.sample.

   Legacy:
   The stats of opentracker could not reflect the real state after I added this function,
   such as count of peers, count of seeds. This is a bug, but it seems that which couldn't
   hamper the downloader to track peer and fetch resource. I'll fix it in a future updates.
3) Re-indent source codes, by OSX command 'indent -br -lp -i2 -nfbs -di1 -npsl -nut'.
Merge branch 'master' of https://github.com/letv-cdn/opentracker