enable logging of http requests/responses

[jgoldhammer]

It would be nice if gitlab4j supports logging http requests and responses via Jersey.
It would allow to inspect the messages transferred to the gitlab server.

[gmessner]

@jgoldhammer
I temporarily added you as a collaborator so you could review and merge the PR when you are ready. Here is the PR:
#229

[jgoldhammer]

Thanks. I have merged it, very well done!
Can you upload this as new version to Maven Central ?

[gmessner]

@jgoldhammer
Thanks for reviewing and merging. Release 4.8.39 is complete, though as you know it may take 24 hours to show up in the repos.