Soft-Index File Store: (local files)-based cache store
- see SoftIndexFileStore javadoc for design info
ISPN-4696 SuspectException kills operation on ClusterRegistryImpl

* Added retry for ClusterRegistry operations
ISPN-3938 AdvancedAsyncCacheLoader.process() concurrency issues

Simplify ExecutorAllCompletionService to track the tasks itself instead of
using an ExecutorCompletionService.