Add startup flag to set miner strategy

[Bushstar]

Summary

• Adds -minerstrategy which can be used to set a miner strategy, this can either be none which is the same as current behaviour or a numeric value, the node will only stake the that number of subnodes selecting from the highest target multiplier downwards. If a target multiplier set is more than the amount left to select then the remaining few are selected randomly from that set.

Implications

• Storage

  • Database reindex required
  • Database reindex optional
  • Database reindex not required
  • None

• Consensus

  • Network upgrade required
  • Includes backward compatible changes
  • Includes consensus workarounds
  • Includes consensus refactors
  • None