SEC-2788: Add @Configuration as meta annotation to @Enable* annotations

[spring-issuemaster]

Rob Winch (Migrated from SEC-2788) said:

This removes the need to state @Configuration when using @Enable* annotations. For example:

@EnableWebSecurity
@Configuration
public class WebSecurity ... {
...
}

can be shortened to

@EnableWebSecurity
public class WebSecurity ... {
...
}