* 增加工作流导出导入功能，前端定时器表达式的秒和分钟的默认值从*修改成0

* 修改工作流导出导入功能由excel改为json减少依赖

* refactor to use SiftingAppender to write Tasks' log

* refactor to use shared CONSTS for TaskLogInfo

* fix refactor bug

* update escheduler-dao unit test

* change log level to debug

* add unit test

* update escheduler-dao unit test

* update escheduler-api unit test

* Remove useless dependencies and add jsp-2.1-6.1.14

* Determine if principal is empty in getJdbcUrl method

* fix bug  when register worker but create master node in zookeeper

* Remove useless dependencies such as hive-shims and log4j

* upgrade commons-email from 1.2 to 1.5 and remove mail-1.4.5.jar

* change log level to debug

* add unit test

* update escheduler-dao unit test

* update escheduler-api unit test

* update escheduler-api unit test

* change log level to debug

* add unit test

* update english documents

* refactor zk client

* update documents

* update zkclient

* update zkclient

* update documents

* add architecture-design

* change i18n

* update i18n

* update english documents

* add architecture-design

* update english documents

* update en-US documents

* add architecture-design

* update demo site

* Remove useless dependencies and add jsp-2.1-6.1.14

* Determine if principal is empty in getJdbcUrl method

* fix bug  when register worker but create master node in zookeeper

* Remove useless dependencies such as hive-shims and log4j

add embedded h2 db and jacoco report plugin for jenkins

add jacoco report plugin for jenkins

add embeded zookeeper for test

ignore some test until find better test method

* Remove useless dependencies and add jsp-2.1-6.1.14

* Determine if principal is empty in getJdbcUrl method

* fix bug  when register worker but create master node in zookeeper

* Remove useless dependencies and add jsp-2.1-6.1.14

* Determine if principal is empty in getJdbcUrl method

 use right desc

remove category x what can we not include in an asf project

Add unit tests for cn.escheduler.common.utils.JSONUtils

* Update EasyScheduler Proposal.md

* update proposal

* only write core dependency

These tests were written using Diffblue Cover.

* Update EasyScheduler Proposal.md

* update proposal

* Update EasyScheduler Proposal.md

* update proposal

* add druid connection provider in order to change quartz default connection pool

* remove c3p0 in escheduler-api and escheduler-dao

* change method name queryByIdAndIp to queryBySessionId and queryByUserIdAndIp to queryByUserId

* change connectionProvider.class from c3p0 to druid

* change connectionProvider.class from c3p0 to druid

fix mail style