Introduced LoggingHttpProxy to be used together with MockHttpServer

I like the simplicity of the mock-http-server implementation but needed a way to log and persist more complex requests/responses which can afterwards be used as mocks with MockHttpServer. So I did quite a lot of changes and MockHttpServer is not backwards compatible anymore... I updated the version to 2.0-SNAPSHOT. 

For more details about my changes see the wiki I created: https://github.com/kristofa/mock-http-server/wiki

If you don't want those changes to be in your repo I'll maintain it myself with new group id.

Thanks for you time!