ISPN-4710 Avoid checking for FileReadLockKey presence when the segment file is non-chunked
ISPN-4805 Raise the default chunk size for the Lucene Directory to 1MB
ISPN-4756 Upgrade to protobuf-2.6.0 and protostream-2.0.0.Alpha3
ISPN-4357 Use a specific cache for managing protofiles