Decrease Neighbor Stats Compression Latency

[vuapo-eth]

#31 already addressed the stats history submitted by the API growing too large. The issue was fixed with https://github.com/iotaledger/ict/commit/13b237a7593d6718ec9054e72bfa70f912fa9887 which compresses the internally available stats history before submitting through the API. The way this is currently done does not scale well though resulting in an increasing timeout and node load when requesting neighbor stats (at least not causing issues in the GUI as before).

By introducing at least one of the following strategies, this timeout latency could be reduced significantly:

• statistical compression: consider only a subset of the history acting as sample for the entire history (e.g. only consider every 5th round and multiply the stats of that round by 5)
• stateful compression: introduce a state so that previously calculated compressions can be reused