NodeService#deleteObject should also clean up inbound references to a node

Resolves: https://www.pivotaltracker.com/story/show/70772942
Add unit tests for new/refactored HEAD, OPTIONS, and POST methods of FedoraNodes

Resolves: https://www.pivotaltracker.com/story/show/70645824
Reduce log level for "normal" HTTP API operations
Merge pull request #348 from futures/log-levels

Reduce log level for "normal" HTTP API operations

Resolves: https://www.pivotaltracker.com/story/show/70816006