etcdhttp: fix logging in raft handler
Merge pull request #1542 from xiangli-cmu/fix_logging

etcdhttp: fix logging in raft handler
etcdserver: fix sender logging
Merge pull request #1543 from xiangli-cmu/fix_logging

etcdserver: fix sender logging
*: clean log.Print

1. only log things by default that the operator of etcd may need to react to
2. put package name at the head of log lines
Merge pull request #1539 from unihorn/195

*: clean log.Print
*: create ID type

This creates a simple ID type (wrapped around uint64) to provide for
standard serialization/deserialization to a string (i.e. base 16
encoded). This replaces strutil so now that package is removed.