Client refactor, Config service integration test.

1. Refactor apollo client code according to  @qmwu2000's comments
2. Add config service integration tests
3. Add some cat events for config service
4. Fix several bugs

bugfix

首页环境切换 & app主页显示app基本信息 & 样式优化

exclude cat in client/config/admin/portal test

Disable cat in test

Enlarge sleep time for long poll unit test

Server side config update push

Add assembly script

Add unique check for app/cluster/namespace

如果环境下面只有一个default集群，则不展示集群列表

Change default namespace to appid itself

Update exception

首页获取的app列表从配置的环境中拿到 & 创建默认的namespace名字用appid

downgrade jetty version to support java 1.7

fix for java 1.7

ut fix

change apollo-core to 1.7

load namespaces handle release NotFountException

Enhance exception process in portal