Add a decorator to handle the caching of objects stored to
and/or read from persistence (bring over from pre-Angular
branch.) Supports the WARP Telemetry Adapter; the absence
of such a cache has been observed to result in significant
latency in instantiating autoflow tabular views for packets.
WTD-644.
Also, include an empty test file to ensure that the added
decorator is included in code coverage estimation (and to
provide a location for tests to be written later.)