refactor AlertMesageEntity
add alert suspend feature and alert recover announcement feature
add unit when sending alert
extract method from AlertManager, add alert http api docs
add SuspendTest
resolve conflicts
change test cases
resolve conflicts
fix bugs
modify the broker-service time
modify the area
modify the handler
Merge pull request #455 from jialinsun/master

fix issue of date format for third party alert mail content
Merge pull request #454 from leonindy/master

add alert suspend and recovery announcement features, add alert http api document
Merge pull request #456 from youyong205/master

refactor code
fix app line chart show issue