sort events successfuly

The order will effective after all actions including list / create
/update
update the main view

the framework of the mail view is finished.
The UI needs to be optimized
!!New new event has sort problem.
Add three options of tags in create/update view
add simple alert when the class is already full

add title and number limitation to details page
simple view

just backup
add different tag in the event item
add send invite and cancel reminder to the participants
remove redundant bootstrap.js