Add support for sqlite3 hook

This is useful for adding backup functionality to SQLite as seen here:

https://github.com/mattn/go-sqlite3/blob/master/_example/hook/hook.go

In that sample, "sqlite3_with_hook_example" is the name of the driver to be registered. I used "sqlite3hook" in my fork as a generic name. Otherwise gorm will use SQLite in compatibility mode.