fix the issue brought by 0.10.0 that Spring related classes are mistakenly loaded via DefaultInjector, which causes exceptions when there is no Spring libraries available.

2 抽离了一个公共父类ApolloProcessor，用来处理反射相关的逻辑。 ApolloJsonValueProcessor,ApolloAnnotationProcessor,SpringValueProcessor都继承它
3 在PropertySourceProcessor中注册自动更新的监听器AutoUpdateConfigChangeListener
4 SpringValue增加isJson字段，表示这个属性是否是Json类型的
5 增加了单元测试

2. Support XML config placeholders
3. Add more tests to cover all kinds of cases
4. Update apollo demo to adapt for auto update functionality

2. Reorganize the feature to provide the ability to inject apollo
configs in Spring Boot bootstrap phase
3. Add more integration tests to cover different scenarios
4. Update apollo-demo to show this apollo bootstrap config feature could
be used with @ConditionalOnProperty