cache using namedb api
The cache should use the generic namedb api, but it's not possible right now for couple reasons:
- No single key - multiple values paradigm, but we probably shouldn't implement it in the API as it's too complex
- Current node serialization is expensive, it would be the best if the "node" was stored in linear memory, and the "rrdata" as well. This way, pickling/unpickling could be as simple as memory mapping. This is important, as the node access is potentially a very frequent operation. Unless we implement this, the direct access + SKMV is the best thing.