Implement KMD block subsidy calculation and validation

[dimxy]

Implement block reward calculation for the KMD mainnet only (see GetBlockSubsidy function in komodod repo).

Add subsidy calculation:

• add block reward
• add miner fees
• add interest contingent on KOMODO_NOTARIES_HEIGHT2
• add KOMODO_EXTRASATOSHI

Add subsidy validation rules for KMD:

• "coinbase pays too much" (block rule)

[dimxy]

implemented in b58b108ec950f31609fea1c3cc92eb95dcabfcda and a0244f639e350b841be09d14f904a9932b485918