Add a privacy section

[rishkwal]

This section should include explanations of the aspects of privacy and fungibility that are tackled by Coinswap. Having some diagrams accompanied with the explanation of traceability, anonymity sets, etc would be great.

[mojoX911]

Lets skip this one for now. We can keep making the doc in the background, but lets not add it in the first release. I have mentioned few pointers on privacy for in the Intro. Thats should be enough for now. An elaborate privacy impact and analysis doc is definitely useful, but not high priority right now.