Add new check that @Bean methods have to be in @Configuration classes

I added a new check that all `@Bean` methods have to be declared in `@Configuration` annotated classes. If the `@Configuration` annotation is missing, Spring will not create a proxy for the configuration class which results in a new bean instance on each call of the `@Bean` method.
To implement this new check I had to add `org.springframework.context.annotation.Bean` as supported annotation type in order to trigger the annotation processor for classes without `@Configuration` annotation.