Separation of client API and resource server support

@oharsta, here is an initial cut at separating client API and resource server support code into submodules with minimal dependencies. I have also made some minor name changes that I hope are acceptable. Please provide feedback as I continue to clean them up further.

I have also added some Jersey support classes for giving access to a proper security context and user principal; however, they are currently dependent on the use of the servlet filter. Because of this, there is code in the Jersey filter that will not be called when the servlet filter responds eagerly with authorization errors. The fix is to copy and adapt the filter code from the servlet filter to the Jersey filter. I will work on this as time permits.

I also plan to add some README content on how to use the new submodules, as having that would have saved me a lot of time. :)