Exclude tombstone resources when getting a resource's children
Ensure generated link headers include an anchor parameter as needed

Fixes https://www.pivotaltracker.com/story/show/81018546
Fix handling of content node version lookup
- Override FedoraBinaryImpl.getVersionHistory()

Resolves: https://www.pivotaltracker.com/story/show/80903880
Add leveldb test dependency to fcrepo-http-api

Resolves: https://www.pivotaltracker.com/story/show/81049318
Merge pull request #561 from fcrepo4/exclude-tombstones

Exclude tombstone resources when getting a resource's children
Merge pull request #563 from fcrepo4/link-anchor

Ensure generated link headers include an anchor parameter as needed
Mark the hash-uri container as a pairtree node, exclude it from Resource#getChildren() requests, and ensure clients can't create 'deep' hash uri resources from a request body