Add new IReadOnlyNodesCollection for NodesCollection (#241)
Add new IReadOnlyNodesCollection for NodesCollection (#241)

Create new read-only interface for NodesCollection

Re: https://github.com/stratisproject/StratisBitcoinFullNode/issues/115
stratisproject/NStratis,MetacoSA/NBitcoin,NicolasDorier/NBitcoin,thepunctuatedhorizon/BrickCoinAlpha.0.0.1,MetacoSA/NBitcoin,lontivero/NBitcoin