Update NodeRdfContext to be more defensive about missing type information
Accept null values for comparing against a calculated checksum
Remove the self-healing-after-fixity-check-failure feature

This feature was only useful for chained cache loaders on a single host
(e.g. not across clusters, and not for other types of binary stores).
Don't expose the underlying content location in the default jcr:content
serialization

The content location may be expensive to calculate (some cluster
configurations), is often unnecessary for day-to-day operations, etc
Refactor FixityResult to take a string to identify a cache, instead of of the whole CacheEntry
Remove the LowLevelStorageService and supporting classes
Refactor CacheEntry classes to wrap a jcr property, whereever it is
stored

- getFixity() should return a collection of fixity results that provide
  one or more fixity results for all copies of the binary data
- simplify the infinispan distributed executation calls for ISPN-backed
  binary stores
Remove unused test imports

- Remove unused import from ServiceHelpers
- Change copyright date to match new checkstyle rules
Remove LowLevelCacheEntry

- This is a follow-on to: https://www.pivotaltracker.com/story/show/70699932