Bounty - Port bitcoin core fee estimator

[dangershony]

The C# node has a fee estimator but its not working and its the old version of the fee estimation.

While stratis does not need one right now it would be nice to have it for for statistical purposes and for future load, not to mention for those using the node with the bitcoin network.

Here is the link to the bitcoin core fee estimator.
https://github.com/bitcoin/bitcoin/blob/bd59c4395c504e7bddbce80048ed65a53fb26f67/src/policy/fees.h

Link to high level description and PR
https://gist.github.com/morcos/d3637f015bc4e607e1fd10d8351e9f41

Useful article.
https://bitcointechtalk.com/an-introduction-to-bitcoin-core-fee-estimation-27920880ad0

[dangershony]

This is in process (currently in review)
stratisproject/StratisBitcoinFullNode#1486