Update to bitcoin 0.28 release

[dr-orlovsky]

@sanket1729 I am ready to do the PR today ASAP, if you are ok with that and haven't started work on it yet.

[sanket1729]

@dr-orlovsky, yes, please. It is much easier for me to review this at a conference than code myself.

[tcharding]

This can be close now with the 7.0.0. release.