t8n tool testing: support --state.reward -1

[winsvega]

please support

--state.reward -1
for genesis state hash calculation (to calculate given state hash without any 0, or non 0 mining rewards)

Thanks a lot lets see which tests do yo pass. but first I need this option. we recently discoverd a bug in the tests that lead to coinbase account not being present in the state with 0 reward touch. (pre EIP150) rules. but this also means that when I calculate genesis state hash, I don't need coinbase account touch on pre EIP150 rules. so -1 means just calculate the stateRootHash of the given state. which I use to process genesis.