Implement prototype for annotation processing

[schlagi123]

Hi Martin,

I have create a prototype for an annotation processor. The changes are in the spring and core (https://github.com/openapi-processor/openapi-processor-core/pull/100) repository.

One open problem is currently the logging. The Project https://github.com/Cosium/annotation-processor-logger shows an solution to use SLF4J. But if in the future a annotation processor is only used or in a special repository for it exists, it is also possible to change the whole logging process to the javax.annotation.processing.Messager class.

In the following Attachment you can see an example of how to use it: example.zip