support spring security oauth 2 default ScopeVoter prefix

Create SecurityConfig instead of WebExpressionConfigAttribute when the token is starting with 'SCOPE'. If not, the plugin will create a WebExpressionConfigAttribute when I have @Secured(['SCOPE_READ']). When calling WebExpressionConfigAttribute.getAttribute(), it always return null and the ScopeVoter is not able to execute the logic in the if block (https://github.com/spring-projects/spring-security-oauth/blob/master/spring-security-oauth2/src/main/java/org/springframework/security/oauth2/provider/vote/ScopeVoter.java#L138)

https://github.com/spring-projects/spring-security-oauth/blob/master/spring-security-oauth2/src/main/java/org/springframework/security/oauth2/provider/vote/ScopeVoter.java#L100