Inline `reward` and `validateScores` for gas

[juliangruber]

Lowers gas by 2-4%

• Removes one redundant loop
• Removes two functions

test_TransferScheduled() (gas: -30928 (-1.225%)) 
test_SetScoresMultipleCalls() (gas: -38387 (-1.580%)) 
test_SetScoresMultipleParticipants() (gas: -36536 (-1.794%)) 
test_SetScoresOverflow() (gas: -32317 (-1.809%)) 
test_SetScoresTooBig() (gas: -32317 (-1.809%)) 
test_SetScores() (gas: -35288 (-1.822%)) 
test_SetScoresFractions() (gas: -36422 (-1.852%)) 
test_rewardsScheduledFor() (gas: -36308 (-1.871%)) 
test_RewardBurner() (gas: -36539 (-1.871%)) 
test_MinBalanceForTransfer() (gas: -36539 (-1.885%)) 
test_Reward() (gas: -36770 (-1.893%)) 
test_SetScoresTooBigHistoric() (gas: -34548 (-1.904%)) 
test_AvailableBalance() (gas: -36539 (-1.906%)) 
test_ReleaseReward() (gas: -36308 (-1.916%)) 
test_AdvanceRoundCleanUp() (gas: -36308 (-1.999%)) 
test_SetNextRoundLength() (gas: -36077 (-2.020%)) 
test_AdvanceRound() (gas: -36077 (-2.021%)) 
test_SetScoresEmptyRound() (gas: -36194 (-2.031%)) 
test_AddMeasurements() (gas: -36077 (-2.043%)) 
test_SetScoresNotEvaluator() (gas: -36077 (-2.047%)) 
test_SetRoundRewardNotAdmin() (gas: -36077 (-2.049%)) 
test_SetScoresUnfinishedRound() (gas: -36077 (-2.049%)) 
test_SetRoundReward() (gas: -36077 (-2.053%)) 
test_GasSetScores() (gas: -267077 (-3.475%)) 
Overall gas change: -1087864 (-2.111%)