[task] changed AuthService to use Jersey
[cleanup] changed to a plain old string for charset name
[cleanup] making final what has to be final
[cleanup] minor refactorings, cleanup
[task] changed AbstractOsiamService to use Jersey
[fix] added apache http client

jersey fails to send PATCH requests with Java HttpUrlConnection, so
apache http client is introduced.
[task] deprecated retrieveAccessToken(HttpResponse)
[fix] using more specialized exceptions in catch clause
[fix] HTTP status 401 requires WWW-Authenticate header