Not all statistics are always available.
GH #175 - Get messages using POST in both JSON and XML.
GH #175 - Updating test cases.
GH #175 - Fixed failing tests.
GH #175 - Identify clients by Basic Auth credentials.
GH #175 - Added acks/rejects.
GH #175 - Invoke REST callbacks with JSON or XML.
GH #175 - Added means for clearing message and in-flight queues.
Don't attempt to access statistics that don't exist.
GH #175 - Fixed tests.
Merge branch 'bring-back-e324b2678eb9a532a9529a7ac3dfc5aee01c7197-from-reflog'