SERVER-15535 add arbiter to make shutdown test work
SERVER-15535 Do not immediately stand for reelection after stepping down for a higher priority node.
SERVER-13635: pass whether an index is unique or not down through SortedDataInterface
SERVER-13635: better txn lines for replication sync
SERVER-15683: add command to introspect OperationContext and RecoveryUnit
SERVER-13635: make test handle oplogs of different engines
SERVER-13635: txn boundary for chunk migration getting disk locs
SERVER-13635: fix race in kv db catalog entry
SERVER-13635: add hook to RecoveryUnit for when we are take out of and put back into service
SERVER-14973 consolidate shard key parsing, cleanup shard key patterns
SERVER-13635 fixed createCollection shell helper to understand storageEngine option
SERVER-15486 jstest fix
SERVER-15486 parse_log_component_settings
SERVER-15486 LogComponentVerbositySetting validation

Implement _set via parseLogComponentSettings.

Also extract most of LogComponentVerbositySetting.append to new method _get.
Remove need to prune mutablebson doc produced by _get.
Replace typedefs with 'using'.
SERVER-13635 take ownership of shard key in shardCollection
SERVER-15683: fix caching of Client when there is none
fix txn read boundaries and locking
SERVER-13635: OperationContext doesn't always have a RecoveryUnit
Merge remote-tracking branch 'nextdoor/master'

Conflicts:
	src/mongo/db/operation_context_impl.cpp
	src/mongo/db/repl/minvalid.cpp
SERVER-13635 (rocksdb) pass whether an index is unique or not down through SortedDataInterface