Create and drop view

[black-06]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

create view #4966

It's different from issue's suggestion.
I found the unimplemented CreateView function in Migrator,
then I implemented it.

About ViewOption:

• Query is a subquey
• If Replace is true, exec CREATE OR REPLACE. sqlite may not support this.
• If CheckOption is not empty, append to sql, e.g. WITH LOCAL CHECK OPTION

User Case Description

DB.Migrator().CreateView("users_pets", gorm.ViewOption{Query: DB.Model(&User{}).Select("users.id, users.name")})

CREATE VIEW `users_pets` AS SELECT users.id, users.name FROM `users`

[a631807682]

Do we need to add parameter checking, such as what happens without option.Query? can we add comments to explain how to use it?

sqlite may not support this.

It doesn't matter, just need to handle it in the sqlite driver

[black-06]

Do we need to add parameter checking, such as what happens without option.Query? can we add comments to explain how to use it?

sqlite may not support this.

It doesn't matter, just need to handle it in the sqlite driver

done ~