Support role permissions per environment

add apollo portal demo with public server.

add admin page to delete app, cluster and app namespace

add delete app namespace api

add delete app api

support passing apollo.meta and apollo.configService via system property, etc

local cache dir customizable

externalize application-github.properties and apollo-env.properties

refactor GlobalDefaultExceptionHandler a little bit

更改非法请求的log级别从ERROR到Warn (2)

https://github.com/ctripcorp/apollo/issues/1209

Support multiple meta servers