Enhancing Difficulty Epoch panel to support pruned nodes. Prior to this it would fail back to a block height of 1 so it could render something and not fail but it was bogus data.
Now it'll estimate the epoch block time based on time from pruned height to the present. Labels will denote that results are no longer as accurate. The rendered blocks mined are inset some for pruned nodes. I may change them to a different symbol
