Record query consumption into fe audit log. Its basic mode of work is as follows, one of instance of parent plan is responsible for accumulating sub plan's consumption and send to it's parent, BE coordinator will get total consumption because it's a single instance.
1. Implement Backend http server using libevent instead of mongoose.
2. Remove Old Hypertable rpc framework, use brpc instead.
3. Change rpc from FE to BE to brpc.
4. Fs broker support HDFS HA.
5. add more metrics to monitor.
6. Lots of bug fixed.
