Added useLastIrreversible to TransactionConfig and default to true.
When useLastIrreversible is true, then blocksBehind will be ignored and the last irreversible block and expiresSeconds will be used to calculate TAPOS.
When useLastIrreversible is false, then transaction processing will take the current head block minus blocksBehind and expiresSeconds and use them to calculate TAPOS.
Fix issue with blocksBehind transaction expiration time. It was previously being calculated from the current head block time rather than the time stamp of the block found using blocksBehind.
Update javadoc and README to include information on useLastIrreversible.
Added useLastIrreversible to TransactionConfig and default to true. When useLastIrreversible is true, then blocksBehind will be ignored and the last irreversible block and expiresSeconds will be used to calculate TAPOS. When useLastIrreversible is false, then transaction processing will take the current head block minus blocksBehind and expiresSeconds and use them to calculate TAPOS. Fix issue with blocksBehind transaction expiration time. It was previously being calculated from the current head block time rather than the time stamp of the block found using blocksBehind. Update javadoc and README to include information on useLastIrreversible.