重命名 activity 相关变量为 event
Create EventDuration Model (Sync with database)
Fix errors for events url mapping
Improve event creation form

1. Separate duration date, start_time and end_time
2. Set default values for duration
Fix mysql chinese characters errors

1. Add notes in readme to create database with collation: utf8
2. Fix url error in user signin and signup form.
3. Update scriptfan and alebic conig file database url
Update event creation.