* [NOD-264] Implemented calcTxSelectionValue.
* [NOD-264] Fixed bad subnetworkID in calcTxSelectionValue.
* [NOD-264] Implemented sorting the txDescs by value.
* [NOD-264] Got rid of txPrioItem.
* [NOD-264] Moved transaction selection to a separate file.
* [NOD-264] Renamed the result object to txsForBlockTemplate.
* [NOD-264] Implemented tx selection.
* [NOD-264] Fixed trying to get the gas limit for built-in subnetworks.
* [NOD-264] Wrote comments where appropriate.
* [NOD-264] Moved calcTxSelectionValue to the mining package. (Non-mining nodes shouldn't be forced to calc selection value for every transaction)
* [NOD-264] Wrote a test for selectTxs.
* [NOD-264] Fixed a comment.
* [NOD-264] Fixed misunderstood test.
* [NOD-264] Added zero fee check. Added a couple more tests.
* [NOD-264] Added probabilistic tests. Fixed a couple of bugs in tx selection.
* [NOD-264] Fixed tests with missing fees.
* [NOD-264] Added a test over a range of txs with different gas/mass.
* [NOD-264] Added expected probability to the rest of the test cases.
* [NOD-264] Tightened bounds in probability test.
* [NOD-264] Fixed values in probabily test.
* [NOD-264] Added a comments for alpha and rebalanceThreshold.
* [NOD-264] Fixed a couple of comments, renamed result to txsForBlockTemplate.
* [NOD-264] Removed an irrelevant comment. Changed Tracef to Warnf in some logs.
* [NOD-264] Renamed selectionValue -> txValue.
* [NOD-264] Moved rebalancing to the start of the tx selection loop.
* [NOD-264] Added overflow check for gasUsage.
* [NOD-264] Renamed blockSigOps and blockMass to totalSigOps and totalMass.
* [NOD-264] Removed the need to pass usedCount to reblanaceCandidates. Also relaxed bounds in a test.
* [NOD-264] Split selectTxs into smaller functions. Also relaxed bounds in a test some more.
* [NOD-264] Added a comment for findTx.
* [NOD-264] Ordered candidateTxs by subnetwork instead of txValue.
* [NOD-264] Disallowed zero tx fees in mempool and config. Renamed iterateCandidateTxs to populateTemplateFromCandidates.
* [NOD-264] Changed isFinalizedTransaction log level from Warn to Debug.
* [NOD-264] Removed references to SigOps in txSelection.
* [NOD-264] Removed SigOps validation. Validating mass should suffice.
* [NOD-264] Renamed wasUsed to isMarkedForDeletion.
* [NOD-264] Renamed markCandidateTxUsed to markCandidateTxForDeletion.
* [NOD-264] Made some probabilistic tests less likely to fail when they shouldn't.
* [NOD-264] Added a message warning people about probabilistic tests.
* [NOD-264] Rephrased a comment about rebalanceThreshold.
* [NOD-264] Removed IsCoinBase, CheckTransactionInputsAndCalulateFee, and ValidateTransactionScripts from txSelection.
* [NOD-264] Removed a condition that is no longer relevant.
* [NOD-264] "which's" -> "whose"
* [NOD-264] Removed wasteful preallocations.
* [NOD-264] Fixed a comment referring to "used" transactions.
