* [DEV-66] fix endless loop in validateParents
* [DEV-166] add TestValidateParents
* [DEV-166] use generateNode in TestValidateParents to avoid repetition
* [DEV-166] use blockDAG.genesis instead of blockDAG.virtual.SelectedTip()
* [DEV-74] Implemented and written tests for utxoIterator.
* [DEV-74] Improved utxoIterator tests.
* [DEV-74] Implemented utxoCollection tests.
* [DEV-74] Implemented utxoDiff and its tests.
* [DEV-74] Implemented utxoSet.
* [DEV -74] Added tests for fullUTXOSet.
* [DEV-74] Added some tests for diffUTXOSet.
* [DEV-74] Wrote tests for diffUTXOSet iterator.
* [DEV-74] Added a negative test for diffUTXOSet.withDiff.
* [DEV-74] Wrote tests for addTx.
* [DEV-74] Wrote a toRemove test for addTx.
* [DEV-74] Changed blockNode.utxoDiff to be of type utxoDiff.
* [DEV-74] Removed superfluous whitespace.
* [DEV-74] Renamed confusing "previousHash" to "hash".
* [DEV-74] Fixed bad test and corrected failing test.
* [DEV-74] Moved confusing "negatives" test to be part of the general utxoCollection test.
* [DEV-74] Removed utxoDiff.inverted.
* [DEV-74] Renamed blockNode.utxoDiff to blockNode.diff.
* [DEV-74] Renamed diff to diffFrom for clarity's sake.
* [DEV-74] Converted the type of utxoCollection from map[daghash.Hash]map[uint32]*wire.TxOut to map[wire.OutPoint]*UtxoEntry.
* [DEV-74] Corrected test names in utxoCollection_test.
* [DEV-74] Removed superfluous utxoCollection iterator and moved utxoIterator into utxoset.go.
* [DEV-74] Renamed variables in utxoset.go.
* [DEV-74] Renamed verifyTx to areInputsInUTXO and removed a superfulous test.
* [DEV-74] Fixed bad test logic in TestDiffUTXOSet_addTx.
* [DEV-74] Added a few comments. Added reference-equals checks to clone functions.
* [DEV-74] Moved utxoCollection and utxoDiff into utxoset.go.
* [DEV-74] Wrote explanations for utxoCollection and utxoDiff tests.
* [DEV-74] Wrote explanations for all utxoSet tests besides addTx.
* [DEV-74] Wrote explanations for TestDiffUTXOSet_addTx.
* [DEV-74] Moved the documentation for utxoDiff into utxoset.go.
* [DEV-74] Wrote an explanation on utxoSet.
* [DEV-75] Found a typo.
* [DEV-75] Renamed dag -> virtual, dagView -> virtualBlock.
* [DEV-75] Renamed newDAGView to newVirtualBlock.
* [DEV-75] Moved queries for the genesis block from virtualBlock to BlockDAG.
* [DEV-75] Got rid of chainView height and findFork.
* [DEV-75] Renamed receivers from c to v.
* [DEV-75] Updated initBlockNode to allow for virtual (headerless) nodes, updated dbDAGState to contain multiple tip hashes, implemented virtualBlock.setTips.
* [DEV-75] Got rid of virtualBlock.equals, which was not used anywhere.
* [DEV-75] Got rid of virtualBlock.tip().
* [DEV-75] Got rid of SetTip everywhere except for tests.
* [DEV-75] Got rid of Next().
* [DEV-75] Got rid of Contains().
* [DEV-75] Got rid of HeightRange(), as no one was using it.
* [DEV-75] Made verifyDAG in rpcserver.go not use block height for iteration.
* [DEV-75] Got rid of the part of Manager.Init() that handled "catching up" for side chains, which allowed me to get rid of BlockDAG.BlockByHeight().
* [DEV-75] Dropped support for the RPC command getblockhash since it was getting blocks by their height.
* [DEV-75] Dropped getnetworkhashps since it was reliant on height, fixed another couple of RPC commands to return nextHashes instead of a nextHash, and got rid of nodeByHeight in virtualBlock.
* [DEV-75] Got rid of setTip().
* [DEV-75] Moved blockLocator() out of virtualBlock and into BlockDAG. Also removed TestLocateInventory().
* [DEV-75] Implemented addTip().
* [DEV-75] Cleaned up virtualblock.go a bit.
* [DEV-75] Erased irrelevant tests in virtualblock_test.go. Moved dag-related tests into dag_test.go.
* [DEV-75] Removed unnecessary nil check.
* [DEV-75] Wrote tests for virtualBlock.
* [DEV-75] Fixed bad test, added explanations to tests.
* [DEV-89] Fixed a comment.
* [DEV-89] Fixed another comment.
* [DEV-89] Removed the section in Manager::Init that handled rolling back indexes to the main chain if their tip is an orphaned fork. This could only happen during reorg, which no longer exists. Also removed BlockDAG::MainChainHasBlock, which was no longer used by anyone.
* [DEV-89] Removed the nil check inside initBlockNode() and amended the one place that called it with nil.
* [DEV-89] Renamed the receiver param for BlockDAG from b to dag.
* [DEV-89] Moved fastLog2Floor from dag.go to btcutil/btcmath.go.
* [DEV-89] Renamed tstTip to testTip.
* [DEV-89] Renamed phanom_test.go to phantom_test.go.
* [DEV-89] Fixed comments, renamed mainChainHeight to dagHeight.
* [DEV-89] Rewrote virtualBlock.addTip().
* [DEV-89] Fixed a comment. (chain -> DAG)
* [DEV-89] Fixed another chain -> DAG comment.
