MX-1224, fix test to pass
MX-1225, pitr test
MX-765, Implement Ark Consensus algorithm
Merge branch 'election3-sandbox'

Conflicts:
	src/mongo/db/oplog.cpp
Update building.md
MX-1223, change rollback algorithm to not require the entire pre-image of a document. Rollback now has multiple phases. First, we scroll back to accumulate the list of documents that need to be updated, then we get a snapshotted version of the affected documents, then we scan forward to the point where the snapshots where taken.
MX-1223, Change as many commands as possible to not go fatal if encountered
during the forward phase of rollback
MX-1223, add error codes
MX-1235, have applier properly crash if it cannot apply an operation 100 times.
Merge branch 'bugfixes/tokumx-1.5'
MX-1223, fix simple bug
MX-1238, have unindexed updates only log the pk and not the full pre-image
MX-1239, remove invertUpdateMods, a dead function
MX-1223, fix bug in RollbackGTIDSetBuilder::initialize
MX-765, fix oplog_upgrade.js after committing Ark
MX-1244, temporarily disable test
MX-765, initialize HeartbeatInfo::highestKnownPrimaryInSet
MX-1244, redo initial_sync5.js.
MX-1207, change the socket timeout of a replication thread to unlimited when replicating a large transaction.
Merge branch 'bugfixes/tokumx-1.5'