* Implement GHOST.
* Implement TestGHOST.
* Make GHOST() take arbitrary subDAGs.
* Hold RootHashes in SubDAG rather than one GenesisHash.
* Select which root the GHOST chain starts with instead of passing a lowHash.
* If two child hashes have the same future size, decide which one is larger using the block hash.
* Extract blockHashWithLargestFutureSize to a separate function.
* Calculate future size for each block individually.
* Make TestGHOST deterministic.
* Increase the timeout for connecting 128 connections in TestRPCMaxInboundConnections.
* Implement BenchmarkGHOST.
* Fix an infinite loop.
* Use much larger benchmark data.
* Optimize `futureSizes` using reverse merge sets.
* Temporarily make the benchmark data smaller while GHOST is being optimized.
* Fix a bug in futureSizes.
* Fix a bug in populateReverseMergeSet.
* Choose a selectedChild at random instead of the one with the largest reverse merge set size.
* Rename populateReverseMergeSet to calculateReverseMergeSet.
* Use reachability to resolve isDescendantOf.
* Extract heightMaps to a separate object.
* Iterate using height maps in futureSizes.
* Don't store reverse merge sets in memory.
* Change calculateReverseMergeSet to calculateReverseMergeSetSize.
* Fix bad initial reverseMergeSetSize.
* Optimize calculateReverseMergeSetSize.
* Enlarge the benchmark data to 86k blocks.
