MIP6 : Governance Subsidy Winner Correction

[SeqSEE]

With MIP5 comes DGPv3 which will solve an issue with governance subsidy winner selection. This means that legacy code can be removed. I have created draft of MIP6

[squidicuzz]

Implemented updates to getGovernanceWinner() which will switch off the legacy code once MIP6 activates. Included in pull request: TheLindaProjectInc/Metrix#197

[SeqSEE]

MIP 6 has been locked in by the network.