Adapt gourd service interface changes
Various improvement to data

1. Fix tag syntax error in data.go
2. Added Password and PasswordHash fields to User
3. Added password field to schema
4. Added a test data SQL file for integration test data
Improve oauth2 to save and load user id

1. Added an oauth2.User interface to get Id from
2. Defined oauth2.apiAuthUser as a dummy
3. User struct implements the oauth2.User interface saves the id to database
4. When loaded from database, UserData will be apiAuthUser dummy with only the id
Implemented login with database

The password is only plain text now.

TODO: need to use hash
Fix the login form target

Left out scope parameter. Added.