Add `EnableDubbo` annotation to dubbo

@EnableDubbo 等价于 @DubboComponentScan 与 @EnableDubboConfig 组合：

示例代码

服务端配置

@EnableDubbo(basePackages = "com.alibaba.dubbo.config.spring.context.annotation")
@PropertySource("META-INF/dubbb-provider.properties")
@EnableTransactionManagement
public static class TestProviderConfiguration {
}

dubbo-provider.properties:

# Dubbo Provider Properties as an alternative for
# Spring XML Bean definition : META-INF/spring/dubbo-annotation-provider.xml

demo.service.application = dubbo-annotation-provider
demo.service.protocol = dubbo
demo.service.registry = my-registry


## Dubbo configs binding properties

### <dubbo:application name="dubbo-annotation-provider"/>
dubbo.application.id = dubbo-annotation-provider
dubbo.application.name = Dubbo Provider

### <dubbo:registry id="my-registry" address="N/A"/>
dubbo.registry.id = my-registry
dubbo.registry.address = N/A

### <dubbo:protocol name="dubbo" port="12345"/>
dubbo.protocol.id = dubbo
dubbo.protocol.name = dubbo
dubbo.protocol.port = 12345

客户端配置

@EnableDubbo(basePackageClasses = TestConsumerConfiguration.class, multipleConfig = true)
@PropertySource("META-INF/dubbb-consumer.properties")
@EnableTransactionManagement
public class TestConsumerConfiguration {
}

META-INF/dubbb-consumer.properties

# Dubbo Consumer Properties as an alternative for
# Spring XML Bean definition : META-INF/spring/dubbo-annotation-consumer.xml

demo.service.application = dubbo-annotation-consumer
demo.service.registry = my-registry

## Dubbo configs binding properties
###  <dubbo:application name="dubbo-annotation-consumer"/>
dubbo.application.dubbo-annotation-consumer.name = Dubbo Consumer
dubbo.application.dubbo-annotation-consumer2.name = dubbo-consumer2

### <dubbo:registry id="my-registry" address="N/A"/>
dubbo.registry.my-registry.address = N/A
dubbo.registry.my-registry2.address = N/A

[mercyblitz]

@willlau0524 本周发布

[willliang1991]

赞，希望Spring Boot相关的使用文档可以更加详细