ZOOKEEPER-1963 Make JDK 7 the minimum requirement for Zookeeper 
(Hongchao via fpj)



git-svn-id: https://svn.apache.org/repos/asf/zookeeper/trunk@1646345 13f79535-47bb-0310-9956-ffa450edef68
netty
code refactor
refactor out findSendablePacket
fix zookeeperTestable
refactor wakeupcnxn
comment and fix testNonExisting
blocking deque
fix findbug warnning
minor logging
convert pendingQueue to List
fix race in cleanup(), iterating and clear
some comments about cleanup()
use netty